I’ll need to know more about your setup to answer that - what os are you currently playing?
Generally the save files located in the game directory can be copied over to a new version and you can continue to play from that point.
If you’re coming from a phone version, I actually don’t know if there’s a way to pull the data off without delving into system files. They are apparently stored at: Android/Data/com.devname.gamename/files - but without a file system viewer you can’t access them, then you have to connect your phone to your pc and transfer the files over using a usb cable.
If you are just switching from the itch version to the steam version on the same system, you have to do nothing - Renpy backs up all game data into a system folder that both the itch and steam version read from. It will find your itch data and pull it into its save folder on steam if it’s the same machine.