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

Here is Why You Need An Adapter

The outlet and plug type used in Niger are C, D, E and F and in Ireland (Eire) is G. This is how they look like.

Ireland (Eire)

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

Type G

Niger

In Niger, outlets of type C, D, E and F are in use.

Type C

Type D

Type E

Type F