Which is the correct metric conversion for mass?

The correct conversion for mass in the metric system is that 1 gram is equal to 1000 milligrams. This relationship is based on the metric prefix "milli-" which denotes a factor of one-thousandth. Therefore, when converting grams to milligrams, you multiply by 1000 because there are one thousand milligrams in a single gram.

The other options represent incorrect conversions based on the standard metric system. Understanding these relationships is crucial for accurate measurement and calculation in healthcare settings where precise dosing and weight measurements are essential.