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

Croatia

In Croatia, outlets of type C and F are in use.

Type C

Type F

French Guiana

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

Type C

Type D

Type E