I don't recognize the SuperFlight name, but if it says the bow is 56" AMO, then get a 56" AMO string. Or, take a cloth tape measure and measure down the back of the bow from one nock, down the limb then all the way across the riser and up the limb to the other nock, following each and every curve. Your actual string length should be 3-4" shorter than what you measure. I'd be gunning for something around an 8" brace height, but that's just where I'd guess it needs to be.