You should probably add the tag for Italian_Roots to your question, Donald.
That project should be able to advise you.
Personally, for my ancestors that migrated after the reunification of Italy in 1861 but before 1946, I used the Kingdom of Italy flag. However, their profile gives the name of their birthplace as it was when they were born: Regno delle Due Sicilie / Regnu dî Dui Sicili (1816-1861) or Regno di Sicilia / Regnu di Sicilia (before 1816) depending on when they were born.
Since Salvatore presumably migrated before 1861 I would use the flag of the Kingdom of Two Sicilies. I just uploaded one (https://www.wikitree.com/photo/gif/European_Flags-1).