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

Here is Why You Need An Adapter

The outlet and plug type used in Namibia are D and M and in Belize are A, B and G. This is how they look like.

Belize

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

Type A

Type B

Type G

Namibia

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

Type D

Type M