You Do Need power plug adapter while traveling from Namibia to Antigua and Barbuda.

Here is Why You Need An Adapter

The outlet and plug type used in Antigua and Barbuda are A and B 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

Antigua and Barbuda

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

Type A

Type B