You Do Need power plug adapter while traveling from Sierra Leone to Côte d'Ivoire (Ivory Coast).

Here is Why You Need An Adapter

The outlet and plug type used in Côte d'Ivoire (Ivory Coast) are C and E and in Sierra Leone are D and G. This is how they look like.

Sierra Leone

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

Type D

Type G

Côte d'Ivoire (Ivory Coast)

In Côte d'Ivoire (Ivory Coast), outlets of type C and E are in use.

Type C

Type E