The symbols r and d represent constants.
The symbol y is the variable.
Do you know how to determine the antiderivative of r^2 - y^2, with respect to y?
If so, then evaluate the definite integral in the usual way by replacing y with the expression d - r (as the upper bound) and with the expression -r (as the lower bound).
If you do not know how to determine the antiderivative of r^2 - y^2, with respect to y, then let me know.
You did not ask any questions. You did not make any statements about what you already know.
Therefore, I am not able to determine at what point in this exercise you're stuck.