No wait, wouldn't it be zero?? Ok, I think you just make the equation equal to zero right? And just solve for R?
When n=3, [itex]\ell[/itex]=0, and m=0 we're describing the 3s orbital which, yes, has two radial nodes. Like you say, a node is where the wave function is zero. As Corribus says, you can fairly easily solve for which values of r the wavefunction is zero.