You Do Need power plug adapter while traveling from Nigeria 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 Nigeria are D and G. This is how they look like.

Nigeria

In Nigeria, outlets of type D and G are in use.

Type D

Type G

Cocos (Keeling) Islands

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

Type I