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

Here is Why You Need An Adapter

The outlet and plug type used in Lebanon are C, D 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

Lebanon

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

Type C

Type D

Type G