Restore a backup from Windows 10 PC folder to iPhone? (there is no backup in iTunes/iCloud)

Where is it exactly? It should be a folder with alpha-numeric name in the ~\MobileSync\Backup folder. Also, have you updated iOS on the new phone? If it's older than on the old phone, iTunes won't allow to restore the backup.

The backup must be in exactly the right location:

Backups in Windows 7, 8, or 10 

To find a list of your backups, go to \Users\(username)\AppData\Roaming\Apple Computer\MobileSync\Backup\

You can also use these steps:

1. Find the Search bar:

• • In Windows 7, click Start. 
  • In Windows 8, click the magnifying glass in the upper-right corner.
  • In Windows 10, click the Search bar next to the Start button.

1. In the Search bar, enter %appdata% or %USERPROFILE% (if you downloaded iTunes from the Microsoft Store).
2. Press Return.
3. Double-click these folders: "Apple" or "Apple Computer" > MobileSync > Backup. 

The backup itself is a folder with thousands of files, and a name with a long string of seemingly random characters. That whole folder must be inside the Backup folder.

In addition, the backup must have been made with the same version iOS that the backup was with, or made with an older version.

When you back up iTunes puts it in the right place. That should be, for you:

\Users\kthug\AppData\Roaming\Apple Computer\MobileSync\Backup\00008101-001979090E60001E

Note that the “point” version must match. So if you had 14.2 on the iPhone 12 you need 14.2 on the iPhone 11. It’s OK if the iPhone 12 had 14.1 and the 11 14.2, but it can’t be the reverse.