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

Here is Why You Need An Adapter

The outlet and plug type used in Mauritania is C and in Mauritius are C and G. This is how they look like.

Mauritius

In Mauritius, outlets of type C and G are in use.

Type C

Type G

Mauritania

In Mauritania, outlets of type C are in use.

Type C