That's what I'm thinkin'
I gave away a few hundred fingerlings a couple of years ago, but the guy I gave 'em to had a large, well established pond.
Tell us more about your pond or pond plans so we have some idea of where to start giving advice. A mature pond with excellent filtration would need to be in the minimum 30-50,000 gallon size range to handle that many Koi at an average size of 10" each.