Please understand that the SI unit for potential energy is the same as the SI unit for all energy, the Joule.The Joule in SI base units is defined as:\\\\(J = \\dfrac{kg \\cdot m^2}{s^2}\\\\)Please consider the equation for kinetic energy.\\\\(K.E. = \\dfrac{1}{2}mV^2\\\\)The units for V is \\\\(\\dfrac{m}{s}\\\\)Square that \\\\(\\dfrac{m^2}{s^2}\\\\)Multiply by the units for mass:\\\\(\\dfrac{kg \\cdot m^2}{s^2}\\\\)Let's consider Gravitational potetial energy:\\\\(P.E. = mgh\\\\)The units for m is kg:\\\\(P.E. = kggh\\\\)The units for g is \\\\(\\dfrac{m}{s^2}:\\\\)\\\\(P.E. = kg\\dfrac{m}{s^2}h\\\\)The units for h is m:\\\\(P.E. = \\dfrac{kg \\cdot m^2}{s^2}\\\\)Lets look at \\\\(E = mC^{2}\\\\)The units for m is kg:\\\\(E = kgC^{2}\\\\)The units for C is \\\\(\\dfrac{m}{s}\\\\) square it \\\\(\\dfrac{m^2}{s^2}\\\\)\\\\(E = \\dfrac{kg \\cdot m^2}{s^2}\\\\)I hope that this helps you to understand that the SI unit for all types of energy is, the Joule.