You Do Need power plug adapter while traveling from Australia 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 Australia is I. This is how they look like.

Australia

In Australia, 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