You Do Need power plug adapter while traveling from Marshall Islands to Åland Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Åland Islands are C and F and in Marshall Islands are A and B. This is how they look like.

Marshall Islands

In Marshall Islands, outlets of type A and B are in use.

Type A

Type B

Åland Islands

In Åland Islands, outlets of type C and F are in use.

Type C

Type F