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

Monaco

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

Type C

Type E

Type F

Niger

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

Type C

Type D

Type E

Type F