Surface area of cylinder = 2πrh
(Top circular surface area not included)

= 2π(r)(2r)
= 4πr²

Imagine the top circular surface area of the cylinder moves to the circular surface of the hemisphere.

Surface area of hemisphere = 2πr² + πr2

= 2π(3r)² + π(3r)²
= 18πr² + 9πr²
= 27πr²

Total surface area
= 4πr² + 27πr²
= 31πr²