You Do Need power plug adapter while traveling from Switzerland 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 Switzerland are C and J. This is how they look like.

Switzerland

In Switzerland, outlets of type C and J are in use.

Type C

Type J

French Guiana

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

Type C

Type D

Type E