Hi! 
To find the volume of a sphere you have to solve an equation, pretty easy once you get the hang of it!
The equation you will need is, V = 

 r³
r³
The first part is 4/3 multiplied by 
 by the radius (half the diameter)
 by the radius (half the diameter) 
So since we do not have the radius, we have to insert the volume in the V variable and solve from there, 
972 
so that divided by 4/3 (3.14) should get you your answer, which is 9
Hope I helped