Hello Steve and welcome to the forums
I don't think that Windows Mail data is included in standard backups. I use Outlook and I have to manually specify Windows to backup the data files, it does not do it by default.
Unless you have changed it, Windows Mail data files are stored in the following folder:
If you restore your backup to a folder, then you could try navigating to the above directory.
I'm sorry to say that I don't think you'll be able to get these details back
There is a chance, but if I'm going to tell it how it is, the chance is very small.