Where do you put the three images? I put them in system but the plugin couldn't find them.
I got it working but It looks like this
I also used region Ids and it didn't help
I never claimed the plugin converts maps to 3D. MV3D is a 3D rendering plugin for RPG Maker MV which can be used to build 3D games.
As you've stated, maps need to be made specifically for MV3D in order to look correct. I can't do magic.