trying to set up my new ipad and we messed up on our passcode, do we need a mac computer to hook it in to reset it

No, you can reset the device with a Windows computer and the latest version of iTunes.

I erased all my older ipad so my wife can use it for ebay sales with larger photos. Her imac is not allowing us to plug the old ipad into it to use the itunes for finishing the startup.The cable works in my charger but not in the imac and we’ve tried all our cables.