grams
There's no "correct" unit. You can use any unit of mass you like, althoughthe gram is sure to result in the most convenient final number.
grams; milligrams
Use centimeters or millimeters.
inches or centimeters
It is measured in grams.
1 milligram
The easiest way would be to have a measuring cup or graduated cylinder and pour enough water into it so that you could immerse a paper clip in the water without it sticking out. Then you drop the paper clip into the water, and measure the difference in how much is in the container. The difference between the two amounts is the volume of the paper clip.
The mass of a paperclip is about one gram. It takes 453.592 grams to equal one pound and 0.453592 kilograms is equal to a pound.
1,000
The international (SI) unit of mass is the kilogram.
The same unit as you use to measure any mass. The SI unit for mass is the kilogram.