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

Here is Why You Need An Adapter

The outlet and plug type used in Benin are C and E and in Niue is I. This is how they look like.

Niue

In Niue, outlets of type I are in use.

Type I

Benin

In Benin, outlets of type C and E are in use.

Type C

Type E