You Do Need power plug adapter while traveling from Guinea to Monaco.

Here is Why You Need An Adapter

The outlet and plug type used in Monaco are C, E and F and in Guinea are C, F and K. This is how they look like.

Guinea

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

Type C

Type F

Type K

Monaco

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

Type C

Type E

Type F