You Do Need power plug adapter while traveling from Falkland Islands 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 Falkland Islands is G. This is how they look like.

Falkland Islands

In Falkland Islands, outlets of type G are in use.

Type G

French Guiana

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

Type C

Type D

Type E