Hi Tina. All Microsoft Office products I've purchased over the years, have all been transferrable or had multiple user clause (to a limit). Since your macbook blew up and caught fire, keep the license. And instal on new macbook. If Microsoft cant help, you need to understand if you have a subscriptions service, or if you have a perpetual license. the former should elicit more help, since they want you to pay again on subscruption. If yours is perpetual, you will have to find your package, email, receipt, or scribble of the 16-20 digit alpha numeric "license key". You may have set up a Microsoft Account when you first purchased the license which may help to know that UserID and PW. On Microsoft wesbsite search for reinstall MS-Excel or MS-Office. You'll be asked to enter the 16 to 20 digit alpha numeric License Key. You may be asked for your Microsoft account UserID and PW. I registered my copy with them by setting up an account I don't use, but it made an easier install for me. when up updated my laptop.4 months ago. Maybe seek help from the merchant that sold you the package can help provide.
Do you have power up capability on old machine, enabling firewire or USB, iCloud, or router connection, to transfer content? or did you save the hard drive or Solid State Drive of the old machine? If so, another option is to pay a local apple certified shop, not affiliated with apple but know the equipment and OS, iOS well enough to do it for you.
good luck.