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

Montenegro

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

Type C

Type F

South Africa

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

Type C

Type M

Type N