Question

need to find outer surface area of the following body

Answer 1

That's too much to help. It would take time. contact @Nnesha

Answer 2

Since the measurements do not have tight tolerances, it is sufficient to approximate/simply the surface area as a revolution of the following figure.

for the surface of the curved and slanted parts, use Pappus' first theorem,
"The first theorem of Pappus states that the surface area S of a surface of revolution generated by the revolution of a curve about an external axis is equal to the product of the arc length s of the generating curve and the distance d_1 traveled by the curve's geometric centroid x_bar."
(see http://mathworld.wolfram.com/PappussCentroidTheorem.html)