You Do Need power plug adapter while traveling from Dominican Republic to Cook Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Cook Islands is I and in Dominican Republic are A, B and C. This is how they look like.

Dominican Republic

In Dominican Republic, outlets of type A, B and C are in use.

Type A

Type B

Type C

Cook Islands

In Cook Islands, outlets of type I are in use.

Type I