Transferring save from GoG to Steam?

So my boyfriend started a save file on my GoG version of Stardew, and he would prefer to buy it on Steam, and was wondering if there was a way to transfer the save, because unless I'm completely blind, I haven't been able to find any physical save file in the system folders.

Could someone please answer or point me in the right direction? ;~;

 

According to the Save File Editing Guide, "Stardew Valley save files are located in your '%appdata%/StardewValley/Saves' folder". (You can copy-paste that string of text into your Explorer location bar or the filename field in an Open dialog and hit enter to jump right to it.)

 

Just to clarify, that means that the GoG and Steam versions use the same location for the saves, and I am pretty certain they're fully compatible. So if you buy it on Steam and run the game, the save files should be available there without any trouble.
...Of course, if you need to transfer it to a completely different computer, then you need to pull the save files from the folder ssokolow mentions and put them in the same place on the other computer