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

Here is Why You Need An Adapter

The outlet and plug type used in Belize are A, B and G 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

Belize

In Belize, outlets of type A, B and G are in use.

Type A

Type B

Type G