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

Here is Why You Need An Adapter

The outlet and plug type used in Hong Kong 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

Hong Kong

In Hong Kong, outlets of type G are in use.

Type G