Setting up the Peering Connection (Project Network) has antiquated terminology and instructions.

Microsoft Entra ID is the new name for Azure AD. The names Azure Active Directory, Azure AD, and AAD are replaced with Microsoft Entra ID. Microsoft Entra is the name for the product family of identity and network access solutions. Microsoft Entra ID is one of the products within that family. https://learn.microsoft.com/en-us/entra/fundamentals/new-name#:~:text=Microsoft  Entra ID is the,the products within that family.

The name change took place on July 15, 2023. https://learn.microsoft.com/en-us/azure/active-directory/fundamentals/new-name

Currently:

Directory/Tenant ID
This is a 32-character alphanumeric string. Find this in the Azure portal in Azure Active Directory / Properties. Show Instructions
Navigate to Azure Active Directory / Properties. Your Directory/Tenant ID is shown under Directory properties.