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

Here is Why You Need An Adapter

The outlet and plug type used in Lesotho is M and in Mauritania is C. This is how they look like.

Mauritania

In Mauritania, outlets of type C are in use.

Type C

Lesotho

In Lesotho, outlets of type M are in use.

Type M