Good! take note this method only works for DPPt, so I hope that's one of the games you wanted to restore to.
You could use the converter in the tutorial's image to convert back to a duc, and replace the file in your folder, I suppose.
Always keep a safe unedited backup before moving things around and editing them.
If your game isn't DPPt, consider using one of the other options to manage NDS saves.