The formula for Circumference is C= πd (with C being Circumference and D being diameter). You would substitute the information into the equation, to find the diameter. After, finding the diameter divide it by 2 to find the radius. When you find the value of the radius, substitute it into the equation (v=4/3πr^3). Volume equals 4 divided by 3, times pi, times the radius cubes (to the power of 3).