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

Jamaica

In Jamaica, 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