How to get coordinates for example inside an object?

Question

Unity

Let's say I have a lot of invisible objects on the level, how can I get coordinates inside them in order to spawn objects there (coordinates should be randomly generated). I apologize in advance if I didn’t write it clearly, it’s just that while I was thinking how to paint it, my head boiled

Answer 1

In general, I just threw an object on each corner and that's it, without these any formulas (:

Answer 2

There is nothing ready, you solve the usual geometric problem about finding a point in the volume of a figure.