Is a sacrificial animal (hady) obligatory for someone who combined Hajj and Umrah, and slaughtered a sacrificial animal (udhiyah) instead of a hady during the days of Mina out of ignorance?

If the reality is as you mentioned, he must slaughter a sacrificial animal (hady) for performing Qiran (combining Hajj and Umrah) in Mecca. He may eat from it, and he may appoint a trustworthy person to slaughter it on his behalf in Mecca. What was slaughtered with the intention of an Eid sacrifice (udhiyah) is not sufficient for this.