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

Mauritius

In Mauritius, outlets of type C and G are in use.

Type C

Type G

French Guiana

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

Type C

Type D

Type E