You Do Need power plug adapter while traveling from Solomon Islands to French Guiana.

Here is Why You Need An Adapter

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

French Guiana

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

Type C

Type D

Type E