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

Here is Why You Need An Adapter

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

Aruba

In Aruba, outlets of type A, B and F are in use.

Type A

Type B

Type F

Saint Helena

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

Type G