You Do Need power plug adapter while traveling from Sint Eustatius to Saint Helena.

Here is Why You Need An Adapter

The outlet and plug type used in Saint Helena is G and in Sint Eustatius are A, B, C and F. This is how they look like.

Sint Eustatius

In Sint Eustatius, outlets of type A, B, C and F are in use.

Type A

Type B

Type C

Type F

Saint Helena

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

Type G