You Do Need power plug adapter while traveling from Montenegro to Rwanda.

Here is Why You Need An Adapter

The outlet and plug type used in Rwanda are C, E, F and G 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

Rwanda

In Rwanda, outlets of type C, E, F and G are in use.

Type C

Type E

Type F

Type G