Here is the method:
- Update Collections app in both old and new device to the latest version
- Plug old device into PC / Mac
- Use iTunes to connect to old device
- Go to File Sharing, and select Collections
- Copy all the folders and files from old device to desktop
- On desktop, change all folders' name by adding suffix ".pkg", e.g. XXX to XXX.pkg (icon will be changed to package)
- Unplug old device from PC / Mac and plug new device into PC / Mac
- Use iTunes to connect to new device
- Go to File Sharing, and select Collections
- Copy all the folders and files from new device if you need to backup
- Delete all the folders and files from new device
- Copy all the folders and files from desktop into new device
- On iTunes, change all folders' name by removing suffix ".pkg", e.g. XXX.pkg to XXX (icon will be changed to folder)
- Unplug new device from PC / Mac
- Finally, launch Collections app in new device
