What kind of lenses can I use for d3000? If I use an adapter to use my fd lenses is it okay? If not why?

I just bought a used d3000, and I have a 50mm, 80-200mm and 70-210mm fd lenses I want to know if using this lenses with an adapter is good or should I just buy a used nikon lens?

If you use an adapter with ANY other lens mount, you'll lose both autofocus and metering, and I wouldn't be surprised if the adapter carried a corrective element (allows infinity focus) which would degrade the image unacceptably in any case.

Try to get hold of at least an 18-55mm AF-S lens that will allow you to use the camera to its full potential.

Such adapters do exist, unfortunately, but are really a huge waste of time. You have a camera designed to be used with autofocus lenses that do not have an aperture ring. Using FD lenses means you have to shoot in full manual mode all the time, and manually focus the lenses. You will find that manually focusing through the tiny dark viewfinder of a D3000 is difficult and not worth the effort. An adapter is also going to lower the image quality of the lenses in use, and will probably add some factor to the focal length, AND some adapters won't let you focus at infinity. They act like extension tubes.

Get Nikon AF-S lenses. The used market has tons of them.

Not a giood idea to use any sort of "adapter" to try to convert lenses of one mount to another mount. You will suffer optical degradation and probably loss of some of the functions.

Did you not think about such matters before getting a cameras body which is not compatible with your existing lenses. If you want to use the lenses then get a compatible camera body. If you want to use the D3000 body then sell the FD lenses and buy Nikon-fit lenses.

Best to go to a good camera store with your camera body and lenses and ask advice. Then you will know that the outfit you buy will work because you will have seen it working in the store!