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

Here is Why You Need An Adapter

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

San Marino

In San Marino, outlets of type C, F and L are in use.

Type C

Type F

Type L

Papua New Guinea

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

Type I