Adding back Mail folders and emails

UArizona wrote:

Was transferring "On My Mac" mail folders to a new computer a few months ago and had some transfer issues. Eventually, I was able to offload about 20 folders of old emails (approx 2GB) to an ext HD. There are 20,000 old emails in folders.

How can I add these back to my current Mail app so they are organized and searchable. I just want them in the "On My Mac" section, with a minimum of effort, and without disrupting my well-tuned current Apple Mail.

Thanks!

Use the import/export function...

if in doubt use the Help menu in your Mail.app tool bar

Import or export mailboxes in Mail on Mac - Apple Support

Mail User Guide for Mac - Apple Support