Is nikkor 70-300mm (non-VR) compatible with d3100?

From what i have read, the Nikkor 70-300mm (non-VR) will not autofocus in the d3100 bust still can i use it? Is it possible that it can damage my d3100 if its not compatible?

You are a bit confused.

What will not auto-focus are lenses that are NOT AF-S or AF-I lenses. NO auto-focus Nikkor lens can damage your fine camera. All of the auto-focus lenses are compatible.

For the whole breakdown of which lenses will perform with which camera, you can visit this link

http://www.kenrockwell.com/...y-lens.htm

Once you get a Nikon dSLR that is beyond the entry level (over $1, 000), nearly all the lenses both auto-focus and AI lenses are usable on those cameras

The lens will mount, the aperture will work properly, you will only lose auto focus. All Nikon auto focus lenses will mount on your camera, many just won't actually auto focus. They will not damage your camera in any way.

Manual focus lenses can be a problem, some will work and some will not. The list on NIkonians explains which manual lenses you can use safely on your camera.