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

Here is Why You Need An Adapter

The outlet and plug type used in Croatia are C and F 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

Croatia

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

Type C

Type F