where are my iMessage on my Mac

Hello steve06174,

We understand you're looking for deleted messages. While there is no means of recovering a deleted conversation from your MacBook the conversation may still exist on other devices. Keep in mind that if you use Messages in iCloud the conversation may be removed there as well: Use Messages in iCloud

Cheers!

In the Catalina messages client (I don't know if this works on Big Sur) in preferences (command ,) within the iMessages tab, there is a button which says 'Sync now'. I cannot guarantee what exact behaviour this would cause with the conversation that is safely stored on the iPad. I would click that button at your own risk.