Goering didn't want "cows like aurochs" - he wanted real aurochs, along with real Tarpan. The idea was that you could "resurrect" an extinct animal by cross-breeding similar animals possessing characteristics of the desired breed.
(That is of course impossible, though you could end up with a very similar species.)
National Geographic made a documentary about these experiments, entitled Hitler's Jurassic Monsters (
). You can watch it here: