STEP 1: find radius $ r $
To find radius $ r $ use formula:
$$ d = 2 \cdot r $$After substituting $ d = 8 $ we have:
$$ 8 = 2 \cdot r $$ $$ r = \dfrac{ 8 }{ 2 } $$ $$ r = 4 $$STEP 2: find volume $ V $
To find volume $ V $ use formula:
$$ V = \dfrac{ r ^{ 2 } \cdot h \cdot \pi}{ 3 } $$After substituting $ r = 4 $ and $ h = 8 $ we have:
$$ V = \dfrac{ 16 \cdot 8 \cdot \pi}{ 3 }$$$$ V = \dfrac{ 128 \, \pi}{ 3 } $$$$ V = \frac{ 128 }{ 3 }\pi $$