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

Here is Why You Need An Adapter

The outlet and plug type used in Slovakia are C and E 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

Slovakia

In Slovakia, outlets of type C and E are in use.

Type C

Type E