Compress the noteook folder as .zip file
Drag the .zip file back to Notes Plus (Documents via iTunes File Sharing (see https://support.apple.com/en-us/HT201301)
Re-launch Notes Plus
Then go to App, then Settings, then Dat Migration,
Make sure you don’t leave the app or let iPad shut down while migration is in progress. Depending on the amount of files you have will depend on how quickly it finishes.
This has worked for me. I have been dealing with duplicates but have had to go to my ICloud and make sure that I have no duplicates there. I made sure I had a copy of my notes and saved it in a separate file so as to not lose them. I then made sure I reinstalled the app and then synced to iPad from cloud. This has given me files I didn’t think I’d get back.
Make sure you You temporarily disable iCloud syncing under Library then Auto Backup and