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

Here is Why You Need An Adapter

The outlet and plug type used in Guyana are A, B, D and G 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

Guyana

In Guyana, outlets of type A, B, D and G are in use.

Type A

Type B

Type D

Type G