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

Here is Why You Need An Adapter

The outlet and plug type used in Cuba are A, B, C and L 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

Cuba

In Cuba, outlets of type A, B, C and L are in use.

Type A

Type B

Type C

Type L