If you're talking about 3D models, then there are various programs you can use to create them. Blender is one that is free, and the paid ones I know about are 3DS Max, Cinema 4D, and Maya.
If that's not what you mean, then I apologise! lol, I don't actually have any experience creating 3D games yet, that's something I want to work on later, or when I get an idea for a good 3D game, so I'm not sure how to get the 3D models from this software into the game engine yet! (although I have seen that there are open source things such as SIO2, which is a 3D game engine I believe, which I'm guessing is one way to do it?!)