A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
If the PC Shop wiped your system, did they re-install Windows for you, and if so, if you go to the Settings App - System - Activation, is Widows indicated as activated correctly?
WIth regards to setting up your accounts, after the PC shop returned your PC, did you log into Windows with the exact same Microsoft account you previously used, and if you used OneDrive previously to sync your files online, have the files re-downloaded onto your PC?
To setup Office (MIcrosoft 365), log into your Microsoft account on this link, you should be able to re-install Office from there without the need for a product key.