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

Here is Why You Need An Adapter

The outlet and plug type used in Cuba are A, B, C and L 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

Cuba

In Cuba, outlets of type A, B, C and L are in use.

Type A

Type B

Type C

Type L