Lens compatibility

I am considering buying a D3100 body. I own a 7 or 8yr old D50. Please advise if my old lens will work on the D3100. I own the following :
Nikon DX AF-S Nikkor 55-200mm f.4-5.6G ED
Nikon DX AF-S Nikkor 18-55mm f3.5-5.6G ED
I am particularly interested if the video autofocus will work with my old lens.
Thank you very much

Both your lenses will work with the D3100 since they both are AF-S.

If you are buying D3100 just because of video autofocus, it is not so good decision.