How Can I Find Out The Serial Number Of Microsoft Office That I Purchased Last Year

They did now reinstall my Microsoft Office, but put it in a folder and told me I had to download it. I downloaded it, however, I do not have the serial number for when I purchased it 1/2010 online. I have no idea where the old email would be.

I can see the original date of setup, Fri. Jan. 8th, 2010. Please advise what are my options. THANK YOU!