The formula for surface area is
SA = 2πr^2 + 2πrh
Where SA means surface area, r stands for radius, and h stands for height.
First find the radius. The radius of a circle is the distance from the outside of the circle to its center. It is half the diameter. To find the radius, divide the diameter by two.
r = 6/2
r = 3 inches
Now plug in the values for radius and height into your formula. Use pi = 3.14
SA = 2(3.14)r^2 + 2(3.14)rh
SA = 2(3.14)(3)^2 + 2(3.14)(3)(8)
SA = 6.28(9) + 6.28(24)
SA = 56.52 + 150.72
SA = 207.24 inches