How many days does it take for an absolute newbie to bike 330km?
Don't do it, unless you're an athletic teenager!  You haven't toughened your backside or your hands to endure riding for hours.  Your lower back, which complements the legs, would develop incredible aches, as would your shoulders, which are used to keep your head up.  The good news is that your knee would probably be fine, assuming that your pedals allow some "float" (right-to-left rotation).  I assume that you have a quality bike that has been recently checked by a mechanic and fitted to you, because little things like the exact seat position matter for long rides.

How much training you would realistically want to do prior to the event would depend upon your age and your state of fitness, but I'd suggest at least a month of riding three days a week.

I've read lots of stories from people who have tried long-distance events with no preparation, and many of them survived, but they all said they wished they had prepared!  You might be able to survive, but would it be an enjoyable experience?  I doubt it...  If the event is coming up soon, I'd recommend to skip it this year and start training for next year's event.