I want to know which type of files are available for the 3D objects in envato elelments
The 3D section of Elements only offers PNGs or PSDs of objects. You basically choose the angle and you get the image.
If you want actual 3D files, then you should use the Envato Marketplace where you buy items individually instead. For example, on this 3D car model item page, it tells you on the right side what you get, so this one includes .fbx, .obj, .mb, and .max. Other items may include different formats, so always be sure to check that.