You Do Need power plug adapter while traveling from Belarus to Vatican City.

Here is Why You Need An Adapter

The outlet and plug type used in Vatican City are C, F and L and in Belarus are C and F. This is how they look like.

Belarus

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

Type C

Type F

Vatican City

In Vatican City, outlets of type C, F and L are in use.

Type C

Type F

Type L