Below is a document which describes the files and format required for a Google Local Inventory feed.
With a local inventory feed, if you have multiple store locations that share the same SKU values a separate store on your account will be required. (The inventory store usually has duplicate SKUs that pan across multiple retail locations so a separate store is required for this feed. See Local Products inventory feed image below).
Find your Store code:
Go to Google My Business > Manage locations > Store code
This link is to give you the setup instructions by Google from the start.