Q: How do I extract an umbrella backup?

I have an old powermac g4 that no longer operates and had a macbook pro that got stolen a few years back - I regularly backed up both of those computers using umbrella to a WD external drive.  I did not transfer any files to my new macbook at the time figuring I could always go back to the external drive if I needed them.  I would like to access the files in those backups but my current macbook doesn't have umbrella.  Any suggestions on how to extract my files?  Any help would be greatly appreciated!