You Do Need power plug adapter while traveling from Mauritania to Ireland (Eire).

Here is Why You Need An Adapter

The outlet and plug type used in Ireland (Eire) is G and in Mauritania is C. This is how they look like.

Mauritania

In Mauritania, outlets of type C are in use.

Type C

Ireland (Eire)

In Ireland (Eire), outlets of type G are in use.

Type G