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

Lithuania

In Lithuania, 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