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

Here is Why You Need An Adapter

The outlet and plug type used in Denmark are C, E, F and K 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

Denmark

In Denmark, outlets of type C, E, F and K are in use.

Type C

Type E

Type F

Type K