Around November 2021 Google My Business is now Google Business Profile
To add or change missing store codes, use your Google Business Profile:
- Sign in to Google Business Profile.
- You will be directed to Google.com with your business profile at the top
- Click on the 3dot menu
- Select Bussiness Profile settings
- Select Advanced Settings
- Near the bottom you will see your shop code, which is your store code for Google Merchant Center