You Do Need power plug adapter while traveling from Puerto Rico 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 Puerto Rico are A and B. This is how they look like.

Puerto Rico

In Puerto Rico, outlets of type A and B are in use.

Type A

Type B

French Guiana

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

Type C

Type D

Type E