How do you plan to move the game to 3d or vr if its made in rpgmaker?
Greetings and hello there.
3d assets and design. some of the character models - particularly in the cut scenes are already in a 3d format and would just require boning and rigging for UE5.
The other stuff is just asset creation and conversions.
In short - it's similar in concept to the classic games of the 90's on the NES (Legend of Zelda comes to mind, which was top down similar to rpg maker), and they had to create the assets to make it into a 3d game. same concepts would apply here.