We have a quarter circle in a square.
Please calculate the volume after rotating the colored part around $BC$ for $360^\circ$. I prefer solutions without calculus but if you could'nt find one without it, mentioning the calculus way is also really helpful.
PS: Don't pay attention to the thing near the AB and AD sides. It means the square side is equal to 3 but it does not matter. You can imagine any size.