if the diameter is 9 units, then the radius is half that, or r = 4.5, therefore
[tex]\bf \textit{volume of a sphere}\\\\
V=\cfrac{4\pi r^3}{3}\quad
\begin{cases}
r=radius\\
-----\\
r=4.5
\end{cases}\implies V=\cfrac{4\pi 4.5^3}{3}\implies V=\cfrac{364.5\pi }{3}[/tex]
