You Do Need power plug adapter while traveling from Solomon Islands to Costa Rica.

Here is Why You Need An Adapter

The outlet and plug type used in Costa Rica are A and B and in Solomon Islands are G and I. This is how they look like.

Solomon Islands

In Solomon Islands, outlets of type G and I are in use.

Type G

Type I

Costa Rica

In Costa Rica, outlets of type A and B are in use.

Type A

Type B