To find volume $ V $ use formula:
$$ V = h ^{ 2 } \cdot r \cdot \pi$$After substituting $r = 6\, \text{cm}$ and $h = 20\, \text{cm}$ we have:
$$ V = 20\, \text{cm} ^{ 2 } \cdot 6\, \text{cm} \cdot \pi$$$$ V = 400\, \text{cm}^2 \cdot 6\, \text{cm} \cdot \pi $$$$ V = 2400\pi\, \text{cm}^3 $$