Resinstall Microsoft office - cant locate lisence key is this on the Apple Mac before I reset ?

I need to reset my Apple Mac Air factory reset due to issues

Ihave saved all my data , but how to I reinstall the Office liscence Word/Excel please

I dont seam to have any emails with the lisence on maybe I did but it was years ago

Can i get this off the laptop? Ask Apple or Microsoft but how been looking and got no where?

I do have Office licence through my work computer should i just use that but if have Apple software dont I need this too?

Any help appreciated thanks so much