Why The prefix milli means one thousandth, so 1000 milliamperes make 1 ampere. Dividing 3000 mA by 1000 gives 3 A. Going from a smaller unit (mA) to a larger unit (A), the number always gets smaller.
Watch out The choice showing 0.003 amperes comes from multiplying by 1/1000 twice, or from confusing 3000 mA with 3 mA; 0.003 A is only 3 milliamperes.
Milli means move the decimal 3 places: mA to A, divide by 1000. 3000 mA = 3 A.