This site will help but I will go over some of the basics here as well.
http://www.mathsisfun.com/algebra/exponent-fractional.html
$$\sqrt6=\sqrt[2]6\qquad \mbox{The 2 is not usually added. It is just understood to be there}\\\\
\sqrt[2]{36}=\sqrt{36}=6\qquad \mbox{because 6 x 6=36}\\\\
Now\;\; \sqrt{36}\;\;\mbox{can also be written as }36^{1/2}\\\\
likewise\;\;\sqrt[3]64=64^{1/3}=4\qquad\mbox{ because 4 x 4 x 4 = 64}$$
etc.
Go to that website and have a look and then come back if you have more questions.
If 0.08" is the diameter then
Go to this page on this site - It is under formulary. (the formula is there plus it will workit out for you.
http://web2.0calc.com/formulary/math/geometry/sphere
Put in radius = 0.04 (half the diameter)
Get you answer.
Multiply you answer by 500
and that is you answer in cubic inches.