Dear Abdulmenan Hussein,

It is very simply: you should divide  capacity loading (mAh/cm2) of your electrode by thickness of the electrode layer (after transformation of nm into cm).

strictly acting, you should take into account the defects which can be possibly formed.

I have a simple dout. volumetric in the sense cm3 but you represented the unit as mAh/cm2

Q = L / h, where: Q - volumetric capacity (mAh/cm3), L - capacity loading (mAh/cm2), h - thickness of the electrode layer (cm).