UrbanCircuit That specific error usually means Windows can't properly read the file system metadata anymore. It doesn't automatically mean your files are gone.
I've seen this happen because of:
NTFS corruption after an improper shutdown.
A failing USB cable or enclosure.
Bad sectors starting to appear.
Disconnecting an external drive while it was still writing data.
I'd avoid copying random "fixes" from YouTube until you know whether the drive itself is healthy.