You Do Need power plug adapter while traveling from French Guiana to Puerto Rico.

Here is Why You Need An Adapter

The outlet and plug type used in Puerto Rico are A and B and in French Guiana are C, D and E. This is how they look like.

French Guiana

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

Type C

Type D

Type E

Puerto Rico

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

Type A

Type B