You Do Need power plug adapter while traveling from El Salvador 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 El Salvador are A and B. This is how they look like.

El Salvador

In El Salvador, 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