here is a good place to start. Since you mentioned you have that machine that reads your FC level you don't absolutely need a test kit, as long as it is able to read higher levels correctly, see if it has a limit. For instance, on that chart the SLAM values is where you would need your pool to be to shock if you ever get algae, and for your CYA that would be 31ppm, see if the owners manual says if that machine can read a high number like that.
https://www.troublefreepool.com/blog/2019/01/18/chlorine-cya-chart/
If your machine can't read high FC levels, you just need this kit to use when you do a SLAM.