I back up to a thumb drive every few months. I also keep the zip files in a separate folder and that gets saved to another thumb drive, then folder then is emptied. The thumb drives are not kept in the house in case of fire.
I back up changed files daily to a thumb drive then I back up everything once a month to an external hard drive
We have an external hard drive, I also use thumb drives and my hubby keeps a company called Carbonite which backs it up for me. i hope you manage to get your designs all backed up soon.
There is a possibility to connect an external hard drive that will back up your data. Or you can move them all to the cloud.
We pay an annual fee to a place called idrive....it runs a backup daily on all our computers plus our website....we call it our piece of mind.....have had to recover our files several times and it was a breeze to do so....