Explanation

Mobility $\mu$ = drift velocity/electric field = $V_{d}/E = (ms^{-1})/(Vm^{-1}) = m^{2}s^{-3}/V$ ($\because$ Volt = $V = \text{joule}(J)/\text{coulomb}(C)$) = $m^{2}s^{-1}C/J = m^{2}s^{-1}$As/$(kgm^{2}s^{-2})$ [Coulomb,c = As] = $kg^{-1}s^{2}A = M^{-1}T^{2}A$