You Do Need power plug adapter while traveling from Puerto Rico to Greenland.

Here is Why You Need An Adapter

The outlet and plug type used in Greenland are C, E, F and K and in Puerto Rico are A and B. This is how they look like.

Puerto Rico

In Puerto Rico, outlets of type A and B are in use.

Type A

Type B

Greenland

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

Type C

Type E

Type F

Type K