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

Here is Why You Need An Adapter

The outlet and plug type used in Finland are C and F 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

Finland

In Finland, outlets of type C and F are in use.

Type C

Type F