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

Here is Why You Need An Adapter

The outlet and plug type used in Equatorial Guinea are C and E 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

Equatorial Guinea

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

Type C

Type E