4.5 A for all the motors.
I think about electricity like it was water flowing through pipes.
A power supply is like a water pump, the voltage is a measure of the 'pressure' that the water(electricity) is pumped into the pipes(wires).
Current is a measure of the amount of water(electricity) that is being pumped.
A power supply will always pump electricity at its rated voltage and can pump an amount of electricity up to its rated amps.
So what you want is a power supply that can pump up to 4 amps of electricty at 1.5 volts.
After you select a power supply maybe you should post again just to make sure its appropriate.