You Do Need power plug adapter while traveling from Slovakia to Cocos (Keeling) Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Cocos (Keeling) Islands is I and in Slovakia are C and E. This is how they look like.

Slovakia

In Slovakia, outlets of type C and E are in use.

Type C

Type E

Cocos (Keeling) Islands

In Cocos (Keeling) Islands, outlets of type I are in use.

Type I