try "Magical Jelly Bean Keyfinder"
ive tested it myself, and it does seem to correctly detect the serial number of the whatever Windows and MS Office application you have installed.
take note though, that since this program deals with serial numbers, some antivirus software may be very strict and would regard this tool as a virus or a PUP (potentially unwanted program). you may want to download and run the program. if you are able to download and run the program, then its fine. but if your antivirus prevents you, you may want to temporarily disconnect from the internet and then disable the antivirus software, and then run the program to retrieve the serial numbers.
afterwards, close the Magical Jelly Bean Keyfinder, run your antivirus app (it might immediately detect and delete "Magical Jelly Bean Keyfinder's exe), and then connect back to the internet.