You Do Need power plug adapter while traveling from Cayman Islands to Niger.

Here is Why You Need An Adapter

The outlet and plug type used in Niger are C, D, E and F and in Cayman Islands are A and B. This is how they look like.

Cayman Islands

In Cayman Islands, outlets of type A and B are in use.

Type A

Type B

Niger

In Niger, outlets of type C, D, E and F are in use.

Type C

Type D

Type E

Type F