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

Here is Why You Need An Adapter

The outlet and plug type used in Congo are C, D and E 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

Congo

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

Type C

Type D

Type E