Use this useful tool to convert surface charge density choosing one of the 6 units of measurment included in this app (with the availability to add custom units), that are:
coulomb/square meter, coulomb/square centimeter, coulomb/square inch, abcoulomb/square inch, abcoulomb/square meter, abcoulomb/square centimeter.
For every units of measurment are also included formulas to convert that unit as you want.