On your keyboard, press the windows key and the R key. (WIN + R)

Doing so will open the search box, There put %appdata% and click on accept.

Demostration:



Then the following location will be opened for you:

(User)>Appdata>Roaming

There select the folder : Stardew Valley

Select the “Saves” folder



Here they look for your farm and select it



Here you will have 4 files, the ones that do not have the “._old” extension are deleted.



The remaining files are renamed, removing the "_Old" termination.



And that would be it, your game will be restored to a save point before the corruption.