You Do Need power plug adapter while traveling from South Africa to Pitcairn Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Pitcairn Islands is I 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

Pitcairn Islands

In Pitcairn Islands, outlets of type I are in use.

Type I