Hey there, don't worry it's a fair question!
Since the previous public version was with a different engine, you can't transfer those saves to this one.
From now on, your previous save files should appear on new versions when you download and install them, but there's a chance they will be incompatible with the newer updates and you may be locked in an unwinnable state since this is not a linear VN. You can still try, but keep in mind it will probably not work quite right.
If it's helpful, new Patreon Updates currently come with a cheat mode that starts you just with the right settings to see the new content, plus the ability to simply see all new scenes directly.