On my My Passport only the latest version is complete in a special Volume folder. The latest changes are kept in a History folder for each version.
I assume the latest files are on the PC. If not, use WD Backup to Restore just the latest version of each file. I think you can select the folders rather than each file. Confirm that each file got to the PC. When you are sure all of the PC files are up to date use WD Drive Utilities to Erase the drive.
Then I suggest you change the backup frequency to Daily rather than Hourly. Every time a new version is made, a History file is created for that version. This is causing the drive to fill up. 1 TB size drive is kind of small for frequent backups.