You Do Need power plug adapter while traveling from Mauritania to South Africa.

Here is Why You Need An Adapter

The outlet and plug type used in South Africa are C, M and N and in Mauritania is C. This is how they look like.

Mauritania

In Mauritania, outlets of type C are in use.

Type C

South Africa

In South Africa, outlets of type C, M and N are in use.

Type C

Type M

Type N