your old work.
There is a distinct possibility that moving directly to Illustrator CC will leave your old work as incompatible with the new version.
Upgrading, albeit slowly, from 9 to CC might be the way to go in that case.
That said, a call to the publisher of Illustrator CC may well be in order here.
I was using Illustrator 9 in Classic environment on an old G4 desktop, but it has died (showing the "panic" screen) and I was thinking of finally upgrading Illustrator to something that will run on my MacBook, which uses OS 10.6.8.
Should I buy the upgrades on Amazon from Illustrator 9 to something close to Illustrator CC or just buy Illustrator CC as if I didn't already own an older version?