You Do Need power plug adapter while traveling from Guinea-Bissau 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 Guinea-Bissau is C. This is how they look like.

Guinea-Bissau

In Guinea-Bissau, outlets of type C are in use.

Type C

French Guiana

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

Type C

Type D

Type E