Rome - the diocese still exists as we know.
Corinth - being an ancient city it has been destroyed and rebuild many times, the one that St. Paul wrote to was destroyed in 375 then rebuild and destroyed a couple of tiem afterwards. Here’s modern day Corinth,
en.wikipedia.org/wiki/Corinth, not sure what diocese it falls under but, it probably is a Greek Orthodox one.
Galatia - was not an actual city but a region in central Asia Minor, or modern day Turkey, there are probably very few Christians living there anymore.
Ephesus - doesn’t exist anymore, in it’s place is a nearby city of Selcuk
en.wikipedia.org/wiki/Sel%C3%A7uk and again there are probabaly very few Christian living there to have their own diocese.
Philippi - is now Filippoi, and it’s a very small village, with a population of just over 10,000, probably not important enough to have it’s own diocese, so it’s probably under another bigger one and probably Greek Orthodox.
Colossae - another city lost to time, at one point it changed its name to Chonae, and now it’s just a bunch of ruins, there’s a nearby modern Turkish town known as Honaz but probabaly very few Christians live there.
Thessalonica - Which has also survived to the modern day, but its church, as I understand it, is now part of the territory that belongs to the Ecumenical Patriarchate of Constantinople.