Lost emails

I have a MAC m1. After upgrading to 14.1, I’ve lost all my emails that were in folders under my inbox (I still have my inbox emails). Some of these folders had very important legal info.

Apple help tried to get them back but it was difficult to understand the tech so I might have missed a step or two of his instructions. When he couldn’t fix problem, he said I needed to talk to google. I’m convinced the loss is due to the software upgrade. (I have 189.68 GB available memory if that helps)

I’m not real savvy with computers.

If someone can help me, I’d appreciate it so much.