Can an iPhone backup folder be retrieved after deletion on Windows?
You sould use some file recovery tools to recover deleted files. Operating system do not delete exact files. Only delete the file references. If you're lucky, OS do not replace your old file's partition with a new file; so you can recover.

iOS only backs up to iCloud and to iTunes, so unless you have another copy of that backup or another computer the device has synced to, you might be left with data recovery on the PC.

Is the iOS device still around to make a new backup?