You Do Need power plug adapter while traveling from San Marino to Cook Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Cook Islands is I and in San Marino are C, F and L. This is how they look like.

San Marino

In San Marino, outlets of type C, F and L are in use.

Type C

Type F

Type L

Cook Islands

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

Type I