Hello @dafaweekgmail.comd ,
At this time, there isn't a way to export specifically bounces from the past 12 months. I've submitted your case to the engineers for further review. If and when they have an update to this feature request, they'll make sure to reach out to you.
In the meantime, I'd recommend going to your Reporting tab, and setting the time frame to be 12 months. Then you can go to each of those emails' specific reporting pages to bring up their individual bounce reports and export / manage as needed.