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

Here is Why You Need An Adapter

The outlet and plug type used in El Salvador are A and B and in Canary Islands are C, E and F. This is how they look like.

Canary Islands

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

Type C

Type E

Type F

El Salvador

In El Salvador, outlets of type A and B are in use.

Type A

Type B