Import "On My Mac" Mailboxes, preserving read/unread

I have mail data from an old Mac saved to an external drive. I know which mailboxes from within that data I'd like to import to my new Mac (Sequoia) under "On My Mac", but I want to make sure the read/unread designations remain intact. I've seen other posts where people say all their emails imported as either all read or all unread. Definitely don't want this. Someone mind providing the step-by-step on how to import as "On My Mac" to get this right? thanks!