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

Here is Why You Need An Adapter

The outlet and plug type used in Malawi is G and in Pitcairn Islands is I. This is how they look like.

Pitcairn Islands

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

Type I

Malawi

In Malawi, outlets of type G are in use.

Type G