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

Here is Why You Need An Adapter

The outlet and plug type used in Sierra Leone are D and G 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

Sierra Leone

In Sierra Leone, outlets of type D and G are in use.

Type D

Type G