Answers (1)
"8.00x3 picometers" is meaningless.
physics.nist.gov/cuu/Units/prefixes.html
You just have to memorize this stuff, at least the ones you work with all the time. It's ok to bookmark the page so you can look up the others when you run across them.
There is a prefix every three powers of ten, except for 100, 10, 1/10, and 1/100. To go from one to another you use the LARD rule: LEFT ADD RIGHT DEDUCT. When moving the decimal to the LEFT you ADD to the power of ten. When going to the RIGHT you DEDUCT from the power of ten.
A picometer is 10^-12 meter, one millionth of a micrometer. Width of human hair might vary from 20 to 180 micrometers, thicker at the base, and certain colors tend to be thinner than other colors.