The saves folder is located at: AppData > Local > VotV > Saved > SaveGames
The "AppData" folder is hidden. To open it, open the "View" tab in File Explorer, then click "Options," and then select "Show hidden files, folders, and drives" in the "View" category at the very bottom.
A more detailed path is: Drive (C:) > Users > (Username) > AppData > Local > VotV > Saved > SaveGames

(Please note that all miniature guides that are not related to VotV are written from the Windows 10 operating system.)

Your Data.sav file and all your saves with worlds are already in the "SaveGames" folder. I recommend creating a file on your desktop and copying all the SaveGames files there to avoid losing them.

You should unzip the .sav files from my archive into the SaveGames folder. If you want, you can change the save mode by changing only the first letter before the underscore: "b_Name" (s - story, i - endless, a - quiet, b - sandbox).
If you don't have the sandbox open, but really need it, replace your Data.sav file in the same folder with the one in the archive (remember to make a backup copy). The Data.sav stores all statistics and achievements, and the sandbox opens immediately after earning the corresponding achievement.

Author: Total Shroomer