STEP 1:
The side of the hexagon is equal the radius of the circumcircle. $$ a = 30 $$
STEP 2: find perimeter $ P $
To find perimeter $ P $ use formula:
$$ P = 6 \cdot a $$After substituting $a = 30\, \text{cm}$ we have:
$$ P = 6 \cdot 30\, \text{cm} $$ $$ P = 180\, \text{cm} $$