how do i find the area of a octagonal prism

The surface area of the two bases  = 4(1 + √2)s^2     where s is the side length of the octagonal base

The surface area of the sides  = 8*s*h    where s is the side length of the octagonal base and h is the height  of the prisim

So...the total surface area =  4s [ (1 + √2)s + 2h ]