On the most basic level, any of those cameras would be a major upgrade for you.
I have some feelings on this, and they favor getting into a mirrorless body early and not be hindered with having to buy 10 year old gear and keep looking through used sales to find even older stuff as the years go by. F-mount DSLR bodies and lenses are now the old way and there will be no new stuff to look forward to. Who still produces a DSLR? Pentax, that's who. But let's review your options presented, then I will present my case on an alternative.
D800e? The oldest option here and I would take the D750 before that option. The one truth in digicams is that newer is almost always better in terms of sensor capabilities. ISO performance gets better with newer generations, pixel count often is higher, and the noise levels with higher ISO improves. But the D800e does have a higher MP sensor than the D750 and the anti-aliasing filter is removed. That does improve sharpness at the cost of potential moire artifacts in some subjects, such as architecture. Helps with portraits and wildlife. It's a trade-off, no free lunch.
I do still have a D750 that is on the shelf waiting to be traded-in for the next Z-mount lens I buy. Personally I loved that camera when I upgraded from a D7000. There was an early recall on production for lower serial numbers, but mine was always good as I bought it at the end of it's run. The tilt screen on the back has been more useful than I first imagined. It can take and use any of the same F-mount lenses that the D800e can, including the screw-drive autofocus types of the 1990's and 2000's. Really a nice option if you want to collect vintage lenses. But I have a reason for not recommending film-era lenses on digicams.
Z50: Newest option, but the lowest MP sensor of the lot. 20MP sensor and it is also an DX crop-frame sensor. Here is where we need to qualify you as far as lenses. It is Z-mount so Z lenses are what you will be shopping for. But the FTZ adapter works well for adapting F-mount lenses to work with it, as long as they are the type with internal AF motors. I have to assume any lens you have currently with the D3000 is that kind since that has the same limitation. Wildlife photographers love the DX cameras since they are concerned with filling the frame with their subjects even more than keeping the ISO noise levels down. But as somebody who has transitioned to full-frame after years of crop-sensor bodies, I cannot overstate how nice it is to work in the ultra-wide range for landscapes and architecture. People argue that you can buy a DX lens as wide as 8mm or 10mm, but have you compared the prices and availability of those against a typical 14mm full-frame lens? I do not see the advantage of a DX camera unless you shoot 75% of your photos with long telephoto lenses.
So a Z50 with the FTZ adapter gives some versatility for future lenses and maybe consider using your current lenses with it. But you are missing out on some sensor ability. I however might make an arguement that your listed interests favor making a switch to full-frame camera body and upgrading to full-frame lenses also.
I did the experiments with using DX lenses on my D750 early on, it is very unsatisifactory. On an optical viewfinder, what happens is that a frame illuminates in the middle of the viewfinder which becomes the frame of the photo. So it's harder to see what you are trying to frame. Just consider that full-frame cameras want to have a full-frame lens, but it is easy to go the other way with full-frame lenses on a DX camera.
My alternate recommendation is going to be the Z5. It is the entry-level full-frame mirrorless body, and as such gets overlooked. It was recently replaced with the Z5II in the new lineup, and yes that is an even better choice if the money is available. The Z5 is nearly the mirrorless version of a D750. The sensor specs out as the same. Most of the other specs are close to each other. Same kind of tilt-screen on the body. Same dual SD card setup, same battery, same accessories to plug-in for the most part. The D750 does have some advantages such as burst exposure speed, 3D AF tracking, and built in scene modes. The 3D tracking and burst exposures are going to play for sports and wildlife subjects. The scene modes I barely tried using on my D750. There is also a difference with the LCD top screen for showing camera settings on the D750 that is not there for a Z5 (or a Z50 for that matter). I do miss that a bit. You are going to want to switch to full-frame lenses. The good news there is that there are basically 3-tiers of full frame Z-mount lenses for individual budgets. DX format Z lenses are all mostly budget-minded and fewer in options.
As of today a used Z5 is about $750+ on KEH's website and a used Z50 up to $500. I think the extra is worth it, but that is about the cost of a lens or FTZ adapter in the difference.
Edit: A few notes I forgot to mention. D750 features a pop-up flash for convenience, this is also there on a Z50. But the Z5 and other full-frame mirrorless bodies do not have built-in flash. They would require a hot-shoe flash. Any hot-shoe flash should outperform a pop-up but that is a thing for trying to add fill-light on an outdoor portrait. Also adapting lenses for Z-mount is very easy. There are 3rd-party mount adapters to fit Sony, Canon, Leica-M, and many others to a Z-body. And manual-focus is stupid-easy on a mirrorless body with focus-peaking visible in the EVF. It literally draws a yellow outline around anything that is currently in focus as you adjust.
