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

Here is Why You Need An Adapter

The outlet and plug type used in Niue is I 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

Niue

In Niue, outlets of type I are in use.

Type I