Save Editors?

first time playing on PC and have played this game so many times, i just want to have fun now. i want lunchboxes lol. only issue is i've tried a few save editors and idk what im supposed to do. my computer won't let me open the files bc i don't think i have the right app for them. what can i download for free (windows) to allow me to edit my saves?

​

thanks!