You Do Need power plug adapter while traveling from El Salvador to Denmark.

Here is Why You Need An Adapter

The outlet and plug type used in Denmark 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

Denmark

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

Type C

Type E

Type F

Type K