You Do Need power plug adapter while traveling from Saint Helena to Turks and Caicos Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Turks and Caicos Islands are A and B and in Saint Helena is G. This is how they look like.

Saint Helena

In Saint Helena, outlets of type G are in use.

Type G

Turks and Caicos Islands

In Turks and Caicos Islands, outlets of type A and B are in use.

Type A

Type B