Hello there,
I do not think this is the right way to purchase the Volume license with KMS. The WindowsLicensing configuration service provider is designed for licensing related management scenarios. Currently, the scope is limited to edition upgrades of Windows 10 client devices, such as Windows 10 Pro to Windows 10 Enterprise.
You can check this article to get the license https://www.microsoft.com/en-in/licensing/default
Volume Activation provides two different models for completing volume activations. Either or both key types may be used by customers to activate systems in their organization:
Key Management Service (KMS) allows organizations to activate systems within their own network.
Multiple Activation Key (MAK) activates systems on a one-time basis, using Microsoft's hosted activation services.
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