A 3D MMORPG is a large undertaking and requires a large amount of programming knowledge and effort. I'm assuming you are new to game development, I apologize if you are not new, so I would say you should check out some programming languages, and start form basics. There are quite a few sites where you can get lessons on popular programming languages.
If you expect to make a 3D MMORPG from RPG maker, you are mistaken. True 3D isn't really possible in RPG Maker.
I hope this helped.
That is all.