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

Here is Why You Need An Adapter

The outlet and plug type used in Brazil are C and N 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

Brazil

In Brazil, outlets of type C and N are in use.

Type C

Type N