You Do Need power plug adapter while traveling from Gambia 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 Gambia is G. This is how they look like.

Gambia

In Gambia, outlets of type G are in use.

Type G

Vatican City

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

Type C

Type F

Type L