Catalog Conversion Failed

My only issue is that I now have two complete sets of media files in two different locations: location A is automatically backed up to the cloud, Location B is not. Unfortunately, the catalog references the media in location B.  Is there a way to  get the catalog to reference the files in location A instead of B? I've considered deleting all the files in location B and then using "Reconnect" but that seems a bit heavy handed ......

Thanks for the suggestions Greg_S they've gone some way to resolving the problem.  To answer your questions first, it's a big catalog, I think, (nearly 30,000 item), and I relinked all the files before attempting the conversion so there shouldn't have been any missing files. 

Unfortunately, I couldn't do anything with the original version 9 catalog because the part conversion had rendered it unusable in version 9 but fortunately I had done a backup prior to attempting the conversion so I was able to use that. At this point thing are a bit vague because I'm sure that I specified restoring to a new location but what actually happened was that the backup got "restored" to the backup location and then automatically converted to Organiser 2020 format.  This was fine and the catalog is now working as far as I can tell except that the media files now seem to be copied into the same location as the catalog which isn't ideal as the originals are in a folder backed up to the cloud whereas the new copies are not, so I've now got to work out how to resolve that conundrum (delete the copies and hope that Organiser can relinks to the originals or delete the originals and move the copies to where the originals were and hope Organiser can follow them) - suggestions welcome!