Hey szak1592.

If you want to go from Cartesian to Cylindrical co-ordinates, you need to use the multi-variable integration by substitution to go from (x,y,z) to (row,phi,z).

The first thing you need are the formulae to go from one space to another and then you can use this to get the Jacobian and finally to get the integral.

I'm guessing you have formulas for this but if not here is the Wiki:

List of common coordinate transformations - Wikipedia, the free encyclopedia