How do I find (if it is even possible) some old emails?

I think those emails might still be on the MS Outlook server and perhaps can be accessed via your external drive, as long as they haven’t been deleted.

However, some servers automatically delete emails if they impose account size or time limits on them.

Outlook stores your emails and other items as a .pst file (I believe the default name is outlook.pst), it would depend on your operating system and how you have the program set up exactly where the file would be on your backup drive.

The easiest way to find it would be to use the windows search features on the old drive/backup you have. (usually if you press the windows key and “F” it will pull up the search)

From there you can point outlook to the old file and, in theory at least, it will allow you to access the old emails along with other information you had stored. (this is covered in the “How to import .pst file data into Outlook” section of the link below)

Here’s a lot more information and step by step instructions from Microsoft.