First, we know our equation for resistivity rho = RA/L. We know that L and A are in [m], which are already in SI units - however, [ohms] are not SI units. We do know, however, we know that R = V/I, and that V = W/Q, where Q=It. This gives us, V = [J]/[A][s], and [J] = [kg m2 s-2]. Plugging this back into our equation for rho = (V/I)(L/A) = [kgm2s-3A-1][m]/[A][m2], cancelling out gives us, [rho] = [kgm3*s-3*A-2].