You have a Microsoft 365 Business Standard subscription and 100 Windows 10 Pro devices.

Subscription Activation is a feature that allows you to upgrade from Windows 10 Pro or Windows 11 Pro to Windows 10 Enterprise or Windows 11 Enterprise without needing a product key or reinstallation. You just need to assign a subscription license (such as Microsoft 365 E5) to the user in Azure AD, and then sign in to the device with that user account. The device will automatically activate Windows Enterprise edition using the firmware-embedded activation key for Windows Pro edition. This method minimizes administrative effort and simplifies the upgrade process. References: Windows subscription activation, Deploy Windows Enterprise licenses