The base SI units are $Kg*m^2/s^2$.
Work Step by Step
Energy is equal to $mass*velocity^2$. The SI units for mass are Kg, and the SI Units for velocity are $m/s$. However, we know that velocity is squared, so the SI Units for $velocity^2$ are $m^2/s^2$. If we multiply this by the units for mass, we get the SI units for Energy, which are $Kg*m^2/s^2$.