.001 ampere = 1 milliampere
The prefix "milli" means "thousandth".
An example you might be more familiar with is 1 millimeter = 1/1000 of a meter = 0.001 meter.
To go from amperes to milliamperes, multiply by 1000. To go from milliamperes to amperes, divide by 1000.
Multiplying by 1000 is the same as moving the decimal point 3 spots to the right. Dividing by 1000 is the same as moving the decimal point 3 spots to the left.
