You Do Need power plug adapter while traveling from Niger to South Africa.

Here is Why You Need An Adapter

The outlet and plug type used in South Africa are C, M and N and in Niger are C, D, E and F. This is how they look like.

Niger

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

Type C

Type D

Type E

Type F

South Africa

In South Africa, outlets of type C, M and N are in use.

Type C

Type M

Type N