Dell Office licenses would have came on a MPI card: [URL] [URL] This is the only location you will get your key. Key finders like Berlarc Advisor do not give the full 25 digit product keys unlike Office 2010 and earlier. Key finders are useless for Windows 10 Home as the free upgrade uses device based activation and the key finders will report a generic product key. See here: [URL] [URL] 
Disclaimer:  I've posted this on several Microsoft "Community Support Sites" and though I have yet to have an actual Microsoft tech support guy address the question, several "MVPs" have, but nobody has yet come up with a totally workable answer, although they have tried. One of the guys who posted something (after I showed him proof that there is such a thing as a Dell OEM-supplied version of MS Office 2013 Home & Business - he originally thought there was no such animal) was that I should "go back to Dell and ask them" so here I am. My original post is copied and pasted below... I've read myself almost blind over the last 3 days and many hours now and I still can't come up with a definitive answer so I'll restate the question:  How do I either back-up the Office Home & Business 2013 "activation file" (or token) or discover and extract the complete Product Key for it?  After I upgraded my Windows 8.1 Professional (32-bit) Dell to Win 10 Pro I've been having horrible crash problems; it's obvious that I'm going to have to reformat and start from scratch. I've managed to get the Windows 10 Pro Product Key using the latest version of Belarc Advisor but I'm hitting a brick wall on my installation of Office Home & Business 2013. Not only is this the Dell OEM version but I've already had to go through Microsoft once to obtain a new (replacement) Product Key due to an earlier problem and since it's the OEM version there's no record of it on the Microsoft "My Account / Office Products" page; apparently if you didn't purchase the Retail version, the Product Key is not recorded there (but it is fully registered and functioning, of course). Per this Microsoft article  [URL]  and the Belarc program I can (and subsequently have) found the last 5 characters of the Key but that's not going to do me any good after the re-install unless I have the rest of them. I've also tried out all of the other "key finder" programs suggested in countless other articles and none of them can find the Key in Office Home & Business 2013, nor have I been able to do so by hacking / searching the Registry.  I simply can't believe that Microsoft did not make some provision for backing up and then restoring a particular "token" file with the necessary info in it or extracting the necessary Key Code so that Office could be re-installed under the current scenario.  Hopefully a MS employee or some other Office Expert can provide some concrete, step-by-step information on how to do this.  Thanks in advance. I am sincerely hoping that the other guys on the Microsoft Forums sent me in the right direction here; that pesky Key Code for Office 2013 has got to be stored somewhere accessible (it's not on any Microsoft server that is accessible by us end-users, that's for sure) and there's got to be some program or methodology around out there to recover and decode the thing so it can be reentered when the program is reinstalled...
How To Backup & Restore the Office 2013 Product Key Or Registration / 
Activation File