How can I obtain the volume of an irregular body if I just know the vertex coordinates of the irregular body?

There isn’t an easy formula, otherwise you would have most likely gotten an answer last time you asked this.

So if you have coordinates for vertices, from there you can start to create regular objects from which to have calculable volumes. And from that you can get to a point where you have measured the volume of the total space.

It is not easy, but it is doable.

And the centroids of the irregular body must be calculated too.

I think @zenvelo has the right idea, divide and conquer. Break the problem into smaller problems that you can solve “calculable volumes”.