You Do Need power plug adapter while traveling from Guinea 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 Guinea are C, F and K. This is how they look like.

Guinea

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

Type C

Type F

Type K

Cocos (Keeling) Islands

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

Type I