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

Here is Why You Need An Adapter

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

Mauritania

In Mauritania, outlets of type C are in use.

Type C

Ethiopia

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

Type C

Type F

Type G