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

Here is Why You Need An Adapter

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

Niue

In Niue, outlets of type I are in use.

Type I

Sint Eustatius

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

Type A

Type B

Type C

Type F