You Do Need power plug adapter while traveling from South Africa 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 South Africa are C, M and N. This is how they look like.

South Africa

In South Africa, outlets of type C, M and N are in use.

Type C

Type M

Type N

Sierra Leone

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

Type D

Type G