Why The prefix milli- means one thousandth, so 1 milliampere is 0.001 ampere and 1 ampere is 1000 milliamperes. Converting from the larger unit to the smaller one means multiplying, so 1.5 x 1000 = 1500 milliamperes.
Watch out The tiny values like 0.0015 come from dividing by 1000 instead of multiplying, which is the conversion you would use going from milliamperes to amperes. The 1,500,000 figure would be microamperes, since micro- is one millionth.
Going to a smaller unit, the number gets bigger: amps to milliamps, multiply by 1000.