Hi,
There will be multiple backup files depending on what you backed up, for example a full backup will include a zip file for each of the following plugins, themes, uploads and database. The text file should be the backup log file which is useful for us to debug when something goes wrong.
To use these files to restore your site you can do one of the following:
Are you able to access wp-admin and the UpdraftPlus settings page?
If so navigate to the UpdraftPlus settings page and click the ‘Existing backups’ tab, here you should see your latest backup and next to it a restore button.
Press that button and follow the on screen instructions to restore your site.
If you are unable to access wp-admin or the UpdraftPlus settings page then another solution is to access your server via FTP, then upload a fresh copy of WordPress to your server and install UpdraftPlus then you can connect to Dropbox again or also upload your backup via FTP to the wp-content/updraft folder.
If you are uploading your backup to your WordPress server then please ensure that you have all of the files from that backup set e.g all the zip files that are part of that backup.
Then again go to the UpdraftPlus settings page and the ‘Existing backups’ tab if you don’t see your backup then press the ‘rescan’ button and then the ‘restore’ button next to your backup.
I hope that helps, if you need any further help or any other question please don’t hesitate to ask.
Best Wishes,
Ashley