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

Guam

In Guam, 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