I want to extend the wires to the motors, what size should i use.

I want to add about 300mm to the motors conductors and I notice there is a big difference in wire size on the motors and the esc’s. The esc’s are 30 amp rated but the motor (2212) wouldn’t draw more than 15 amps, so my question is. If the motor draws 15 amps is that 5 amps in per phase? I need to determine what wire i should use.