Well, let’s say the typical minimum diameter of a burger patty is 2 inches, and the typical maximum diameter is 6 inches, with a mean of about 4 inches:
That would mean that, depending on the diameter of the patty, and assuming all patties are the same diameter, 1 kilometer equals approximately 6 562–19 685 burger patties, with a mean of 9 843.
(All values were rounded up to the nearest integer.)