You Do Need power plug adapter while traveling from Papua New Guinea to Guinea.

Here is Why You Need An Adapter

The outlet and plug type used in Guinea are C, F and K and in Papua New Guinea is I. This is how they look like.

Papua New Guinea

In Papua New Guinea, outlets of type I are in use.

Type I

Guinea

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

Type C

Type F

Type K