The area of a square can be found with the following formula:

Where "s" is the length of any asi of the square.
In this case, you can identify that:
![s=3\operatorname{cm}]()
Knowing the value of "s", you can substitute it into the formula:
![A=(3\operatorname{cm})^2]()
Finally, evaluating, you get that the area of each face of the given cube, is:
![A=9\operatorname{cm}^2]()