Changing platforms to 3D in a 2D platformer - how to approach this?

I'm thinking of changing my 2D platformer a bit - by changing the 2D platforms to 3D.

Basically, the only thing that I want to transform to 3D are platforms and moving the camera under a certain angle to accomodate the new 3D platform visuals. Everything else - player, enemies, environment details (trees, rocks) will stay 2D.

How could I approach this? Is it enough to create 3D platform prefabs and use them instead of existing ones and play with camera position or is there more to it?