The above is known as recursion which is the process of a function calling itself from within the same function. There is a special requirement in recursion called a base case which we won't go into right now. It's more important that you see it cannot be applied to this problem.
Recursion will come up in advanced topics, but not until then so set this concept aside and focus on the problem at hand.
Our function is to return the cubed value of the number given in the argument. Your code is nearly correct, in that you have ** 3 which is the right exponentiation. However, we wish to cube the number, and return it, not pass it back to the function.
return number ** 3
In the above. number does not need to be parenthecized.