You Do Need power plug adapter while traveling from Chad 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 Chad are C, D, E and F. This is how they look like.

Chad

In Chad, outlets of type C, D, E and F are in use.

Type C

Type D

Type E

Type F

French Guiana

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

Type C

Type D

Type E