The program that came with your camera VeiwNX2 will convert it. If you are not planing to doing much post processing then you can set your camera to just shoot in JPEG or you can shoot in JPEG + RAW
Its 100% free (not trial software, but REAL 100% full functional freeware), fully supports a huge range of RAW/NEF formats along with other specific camera and image formats, batch processing and so. Supports Photoshop plug-ins for basic filtering of images in a batch and a lot more