You Do Need power plug adapter while traveling from Solomon Islands to El Salvador.

Here is Why You Need An Adapter

The outlet and plug type used in El Salvador 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

El Salvador

In El Salvador, outlets of type A and B are in use.

Type A

Type B