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

Here is Why You Need An Adapter

The outlet and plug type used in Cuba are A, B, C and L 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

Cuba

In Cuba, outlets of type A, B, C and L are in use.

Type A

Type B

Type C

Type L