microsoft office 2013 professional product key

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. My original post is copied and pasted below. 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.

Microsoft office 2013 professional product key