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

San Marino

In San Marino, outlets of type C, F and L are in use.

Type C

Type F

Type L

French Guiana

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

Type C

Type D

Type E