How do I delete "On my Mac" contact cards?

[TuckerdogAVL]

I'd like to delete the entire list, but now I'm trying to "just simply" delete one card. SOMEHOW (have no clue) 180 people, their phone numbers and addresses, have all been merged onto one card. So anytime I get anything from anyone now, every email comes from "AAA" (the first name/company on the card). When I click to delete it automatically repopulates. It isn't in my icloud. It is in the "On My Mac" which I haven't a clue as to how to access or find.

Thanks.

 

[Satcomer]

This tells me your trying to sell your Mac, is that correct?