The only version of Office on the App Store is Office for iPad. Microsoft does have digital versions and defaulted to this for anyone buying from the Home Use Program. The download would be a .dmg file for the Mac, a sort of .iso equivalent.

Checking my NAS, the .dmg (or the CD if it was a physical disc) had an installer on it. Office 2004 had offered people the choice of using an installer, or dragging and dropping the apps they wanted.