To find radius $ r $ use formula:
$$ V = \dfrac{ r ^{ 2 } \cdot h \cdot \pi}{ 3 } $$After substituting $ V = 1309 $ and $ h = 8 $ we have:
$$ 1309 = \dfrac{ r ^{ 2 } \cdot 8 \cdot \pi}{ 3 } $$$$ 1309 \cdot 3 = r ^{ 2 } \cdot 8 \cdot \pi $$$$ 3927 = 8 \cdot r ^{ 2 } \cdot \pi $$$$ r ^{ 2 } = \dfrac{ 3927}{ 8 \, \pi } $$$$ r ^{ 2 } = 1250.004 $$$$ r = \sqrt{ 1250.004 } $$$$ r = 35.3554 $$