You Do Need power plug adapter while traveling from Western Sahara 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 Western Sahara are C and E. This is how they look like.

Western Sahara

In Western Sahara, outlets of type C and E are in use.

Type C

Type E

Sierra Leone

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

Type D

Type G