The very first problem I can see is the simple typo. Java is case sensitive language, so “cube” and “Cube” mean completely different things. Solution: 1) Please be consistent, and 2) Please use names starting with the lowercase letters for method names as per your Java style guides.
The second problem is due to your method signature for a Math.pow; please see the javadoc. It seems it returns the result as the double. You then try to return the double as the int, and that is a incorrect conversion.
So the solutions is as below:
return b * b * b; // i.e. please don't use `pow`.
return (int) Math.pow(b, 3);
Hope this solution solves your problem.