You Do Need power plug adapter while traveling from Namibia to Martinique.

Here is Why You Need An Adapter

The outlet and plug type used in Martinique are C, D and E and in Namibia are D and M. This is how they look like.

Namibia

In Namibia, outlets of type D and M are in use.

Type D

Type M

Martinique

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

Type C

Type D

Type E