Perimeter is simply the sum of all side lengths...
In this problem you have the circumference of a circle with a radius of 4m and two sides of length 8m. Since the circumference of the circle is 2πr the perimeter is:
p=2πr+2s, given r=4 and s=8
p=8π+16 m, and since they want you to approximate π as 3.14
p=8(3.14)+16 m
p=41.12 meters