Use this useful tool to convert surface current density choosing one of the 7 units of measurment included in this app (with the availability to add custom units), that are:
ampere/square, meter, ampere/square centimeter, ampere/square inch, ampere/square mil, abampere/square centimeter, ampere/cicular mil.
For every units of measurment are also included formulas to convert that unit as you want.