Find the area of a surface (double integral)

I am having some trouble with this problem. It states that I must find the area of the indicated surface of:

The part of the cylinder x^2 + x^2 = 9 that is directly over the rectangle in the xy-plane with vertices (0,0), (2,0), (2,3), and (0,3).

I'm still kind of sketchy on how to draw 3-dimensional objects on an xyz-plane, but it's obviously fairly obvious how to draw the rectangle given the points. However, how exactly do I know what part of the cylinder is within that rectangle? Plus, the formula to solve this kind of problem, I think is...

S = integral

A(G) = SS sqrt(fx^2 + fy^2 + 1) dxdy

There is no y in this function, what do I do? Thanks.