[TWCReborn]

Anyhow you are not looking for the electron's radius. Electron's don't have a radius. Classical models give electrons a radius. Seeing that you have n and l in the equation, I presume you are talking about the <r> (expectation value) of a hydrogen atom? The wavefunction in question, is probably the wavefunctions for the hydrogen atom (Ym,lR). Laguerre is in any introductory QM book if that is what you are looking for. You would simply sandwhich r between your wavefunction and its conjugate and integrate. The setup should be immediately obvious once you look through relevant equations. The rest is fiddling with the math (calculus tricks).

The integrals in these types of problems can sometimes be simplified by considering their parity (odd/even). I don't think this is one of those. Anyhow, beyond setting up the integral, the rest is calculus, so asking someone for an answer is like asking them to do an integral.