How do I get deleted emails back from iCloud

Unfortunately, you don't. If you deleted an email on your iPhone, it was also deleted from your iCloud backup.

Contact your mail service provider to see if they might have a site that will allow you to log on and possibility retrieve old deleted emails.

When you delete an email it is moved to a Trash folder, where you can view or recover it. If you delete it from the Trash folder it is gone forever.