You Do Need power plug adapter while traveling from Niue to Trinidad & Tobago.

Here is Why You Need An Adapter

The outlet and plug type used in Trinidad & Tobago are A and B and in Niue is I. This is how they look like.

Niue

In Niue, outlets of type I are in use.

Type I

Trinidad & Tobago

In Trinidad & Tobago, outlets of type A and B are in use.

Type A

Type B