they won't have one, very few stores stock them. Be careful, they mat try to sell you a different kit saying " it's the same thing". It's NOT.
If all you have ever used is pucks and granular chlorine it is almost impossible for your CYA to be zero unless you recently filled the pool with water. Solid forms of chlorine at about 50% CYA.
Pool store testing is usually poor on a good day, usually useless.
You are at a point where you need to make a decision, follow the pool,store advice or follow the TFPC method. Listening to both will not work.
I would say order one of the recommended test kits now and take control of your pool care. The folks here will teach you the methods, but more importantly give you the knowledge of what is happening in your pool.
Good luck