You would measure a nickel in a Graduated Cylinder. Coins are normally measured in grams for weight and mm for diameter and thickness. A U.S. nickel weighs 5 gm, is 21.2 mm in diameter, and is 2 mm thick.
I would use millimetres to measure the diameter of a thumbtack (commonly known as a drawing pin in the UK). The instrument depends on whether you want the length, in which case a ruler will work, or the width of the shaft, where a vernier caliper or micrometer would be better.
First of all it's "What unit of measurement would you use to measure the diameter of a drink can?" Secondly you would probably use either centimeters or inches, depending on where you are in the world.
Volume of cylinder is pi x r x r x L Value of pi is roughly 3.1415 and you already know the diameter, so you can find the radius which would be half of the diameter. The length is also known. Can you do the multiplication, as that would give you the volume of the cylinder in cubic inches