You Do Need power plug adapter while traveling from Cocos (Keeling) Islands to Martinique.

Here is Why You Need An Adapter

The outlet and plug type used in Martinique are C, D and E and in Cocos (Keeling) Islands is I. This is how they look like.

Cocos (Keeling) Islands

In Cocos (Keeling) Islands, outlets of type I are in use.

Type I

Martinique

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

Type C

Type D

Type E