You Do Need power plug adapter while traveling from Mexico 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 Mexico are A and B. This is how they look like.

Mexico

In Mexico, outlets of type A and B are in use.

Type A

Type B

French Guiana

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

Type C

Type D

Type E