You Do Need power plug adapter while traveling from Northern Ireland 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 Northern Ireland is G. This is how they look like.

Northern Ireland

In Northern Ireland, 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