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

Isle of Man

In Isle of Man, 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