Photoshop 7 is only compatible with Camera Raw 1.0.
Camera Raw-compatible Adobe applications
Why doesn’t my version of Photoshop or Lightroom support my camera?
To open, Raw files from the Canon 6D you need Photoshop CS6, CC or CC 2014. Adobe no longer sells CS5 or earlier.
Or, you can download the free Adobe DNG converter
Photoshop Help | Digital Negative (DNG)
Use that to convert all Raw 6D files to DNGs then try opening the DNGs in Photoshop 7.