Help, Failed MBP got hard drive, and backup

Hi all,
my 2009 MBP failed with some thing wrong, got it replaced.

Now ive got a time machine backup all installed and running fine, and got the old hard drive which ive got in a caddy and running.

Issue: OFFICE:Mac
Now its asking me for the product key.
Purchased it via work offer which emailed the key, and me.com has auto deleted it and i can find the key.
any idea what file i can restore the key with?

Dave

That worked mate, thank you so much indeed