Hello
The key usually comes in a separate email after confirmation email, and this email can arrive up to 48 hours later.
However, it is also digital license, so your Microsoft account iself can work as license.
If it has been 48 hours, you can contact support to ask for the key as well.
To get help, open the "Get Help" app on your computer (just search for it in the Start menu). or go to https://support.microsoft.com/contactus, Type "Billing" and press Enter. On the next screen, click "Contact support" at the bottom of the page, then choose "Windows" > "Manage my subscription". You’ll then see the option to chat with a Microsoft support agent.