Understanding A* Pathfinding

My objective is to be able to bring the character from 1 level to the another. My object is exported from Maya, so I’m not sure if layered graph will work. I’ve tried the tutorial of a single level and it works nicely. I’ve tried playing around with it, but I’m unable to find any tutorial around.

This is how my object looks like:

I’m trying the Recast Graph, or is there a better solution/tutorial for me to approach? The final product I would have to make would be a simple mall, whereby when i click a shop, the player will be able to move to that shop, irregardless of different levels/floor. All object will be done in Maya.

I have Pathfinder Pro, but I’m not sure if i’ve installed correctly. Purchased but when i entered the serial, it does nothing. But i’ve downloaded the Pro version.