neither Turbotax nor the IRS keeps returns that old. I don't think the forms are available online or by phone so you'll have to request them by mail
do your best. I would also attach a statement that says "actual tax documents from 2006 are not available. i used my best effort to estimate the amounts reported"
are you sure it's actually from CA FTB, I mean almost 15 years is a long time for them to wait?
There is no Statute of Limitations with California FTB if you failed to file a 2006 return in the first place.