You Do Need power plug adapter while traveling from Guam to Canary Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Canary Islands are C, E and F 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

Canary Islands

In Canary Islands, outlets of type C, E and F are in use.

Type C

Type E

Type F