Welcome to TFP!
Home page on the left side. Click the 'Pool Calculator" link. Plug in your gallons at the top and enter your values in the fields. It will tell you exactly how much of what to add to your pool. There is no way of knowing how much chlorine you will need in your pool until it is refilled and the new CYA level is known.
What sort of test kit do you have? I don't know of any test kit that can give a CYA level reading of greater than 100 ppm. If you are using a pool store to test your water for you, you need to invest your own high quality test kit. The TF-100 (link in my sig) is the best deal on the market. The Taylor K-2006 will suffice too. Pool stores are notorius for bad test result variances. Their goal is to sell you products and not to keep you trouble free.
Be careful with big time pool draining projects. If your water table is high, you can really run into problems by draining or nearly draining your pool. If there is any question about where your water table sits, it is best to drain in stages rather than in one fell swoop.
Have you read the pool school articles yet? There is information in there that is indispensable.