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

Here is Why You Need An Adapter

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

Aruba

In Aruba, outlets of type A, B and F are in use.

Type A

Type B

Type F

Namibia

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

Type D

Type M