If no one knows it off-hand, I can make the effort later today of going through all the DJH/DH/DTNG eps and counting to figure it out

Actually do you know for sure he reached 200? If the list of characters' 100th appearance is accurate, he'd have been short by 3 episodes. (I'm pretty sure the list shows first the episode where the character reached their 100th appearance and then the number of episodes total the character was in). Unless it hasn't been completely updated, Archie would have only been in 197 episodes.

Snake is in 256 episodes in the Degrassi franchise

Okay, did you count them yourself or do you have a source for that? If you have a source I'd like to see it and maybe we can put the link on either Snake's page or the 100th appearance page. If you counted yourself, did you count all of DJH/DH/DTNG/etc? It's possible that the 100th appearance page is only considering DTNG and later, though it can certainly be updated and changed.

This goes for all of the episodes Snake appeared in throughout the franchise

Okay, I checked the page again and I do think it's only counting his appearances in DTNG and onwards, meaning If This Is It is his 100th appearance only counting the DTNG episodes.

His DH appearances count as well

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.

Aight bet