Restoring to the SAME device after an uninstall or factory data reset:

The app's backup file will not be removed if the app is uninstalled, but will likely be removed if a factory reset is performed. Before performing a factory reset, copy the backup file from your Downloads folder to another location not on your device.  It is named "Ultimate To-Do List Backup.zip".

To recover your data, reinstall the app.  When the opening screen appears (which asks what type of account you would like to sync with), choose the option to restore from the backup.  The app will ask you to browse and select the backup file.  This is in the Downloads folder by default, but you can also access it if it was placed 00

Restoring to a NEW device:

If your device is replaced or upgraded, you will first need to copy the backup from your old device to the new one.  The backup file is located in your Downloads folder and has the name "Ultimate To-Do List Backup.zip".  You can copy the file using any method of your choice, such as transferring it from your old device to a computer, and then back to your new device.  Or, you can upload the file to cloud storage (Google Drive, Dropbox, etc.) and then download it to your new device.  On your new device, the file can be placed at any location you wish.

Once the backup file is copied, install and run the app on your new device.  When the opening screen appears (which asks what type of account you would like to sync with), choose the option to restore from the backup. The app will ask you to browse and select the backup file.