Why do you need the Customer Number for Apps?
If you have access to Apple Business Manager, then login and follow these steps to license apps:
1: From the sidebar, select Apps and Books
2: In the Search field, enter the name of the App that you want to license
In the above example, the app is available on both macOS and iOS. Select the result that is proper for your target operating system.
The right panel will update. Complete the form by
a: Selecting your VPP location. Most ABM instances have one (default).
b: Enter the quantity you are licensing... remember 10 * $0 == 100 * $0. If you have 10 devices, license more than 10 copies as the likelihood that you are going to add an 11th, 12th, 13th, device is probable. For free apps, always license more than you need so you don't have to keep coming back as your fleet grows.
c: Press the Get button.
d: Wait about 10 seconds for the bottom of the page to display the successful license acquisition
Repeat these steps for each app.
Now, you do not mention the MDM that you are using. I will assume you exported the VPP token to the MDM. Each MDM differs in the time it takes to poll ABM. Wait a little while and then log into your MDM. Your apps should be visible for assignment. Deploy them to your enrolled devices.
Hope this helps.
