To find the volume of a sphere as a function of its circumference you need to know the following formulas:

Volume of a sphere is V= `4/3 pi r^3` (1)

Circumference of a sphere C= `2pir` (2)

Manipulating (1) we get `r=C/(2pi)` (3)

Using relation (3) in (1) we obtain `V=4/3pi (C/(2pi))^3=4/3piC^3/(8pi^3=)C^3/(6pi^2)`

You can use Maple to define and evaluate the function.