3D level generator on a grid C#

Hello Unity peeps! I have been researching and trying to figure out for the last couple of days how to go about creating a 3d level generator on a grid.

https://www.youtube.com/watch?v=g6cxOVn9wRU

I saw the game in the video and I believe that they use prefabs and randomly pick a prefab every time, but I was thinking it would be nice to figure out how to program it to generate itself since it would take a bit of time to create a bunch of level prefabs by hand.

What I want to go for is a 3d tile level generator that would run through at runtime have a start and end point and on the edge have a chance to spawn a building you can enter or maybe just some walls or something interesting.

I am not sure the best way to go about this so any advice, tips or a pointer to the right direction would be nice. I assume I would need to create a grid and have an empty gameobject run through the points of the grid and layout prefabs at random but I am not totally sure.

Anyways anything helps! I still consider myself a beginner programmer but I have been doing this for two years now.

Thanks all in advance for the help!