I think the page "List of Characters' 100th Appearances" is (currently) only counting DTNG and onwards though.
From the page: "With 197 episodes (TNG), Archie is the male (and overall) character with the highest episode count in the series." So right now it's not including DJH/DH. It should make it easier to figure out his 200th episode, though, if we look at If This Is It as his 100th episode in just DTNG. I'm guessing it'll be somewhere in Season 9 or maybe Season 10, since if he has 256 appearances total, that means he has 59 appearances in DJH/DH. That would make If This Is It his 159th appearance between DJH/DH/DTNG.