To find radius $ r $ use formula:
$$ V = \dfrac{ r ^{ 2 } \cdot h \cdot \pi}{ 3 } $$After substituting $ V = 3052.08 $ and $ h = 12 $ we have:
$$ 3052.08 = \dfrac{ r ^{ 2 } \cdot 12 \cdot \pi}{ 3 } $$$$ 3052.08 \cdot 3 = r ^{ 2 } \cdot 12 \cdot \pi $$$$ 9156.24 = 12 \cdot r ^{ 2 } \cdot \pi $$$$ r ^{ 2 } = \dfrac{ 9156.24}{ 12 \, \pi } $$$$ r ^{ 2 } = 242.8768 $$$$ r = \sqrt{ 242.8768 } $$$$ r = 15.5845 $$