well if its 1ml then on a 100 insulin pin to get 500iu it will be 8 on a insulin pin(100)or(1cc) which would give you 416.5iu which is preatty close maybe go up to 9 or 10 on the pin.
Not to sure of a 50 pin but i would assume it would be the same since a half of 50 (.5cc) would be 2500iu's