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

Cuba

In Cuba, outlets of type A, B, C and L are in use.

Type A

Type B

Type C

Type L

Cocos (Keeling) Islands

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

Type I