If your TFS server is configured to use Git, you don’t need any extension. The Azure Repos extension will add Pull Request support in Visual Studio Code, but isn't required.
If your TFS server is configured to use TFVC you need to install Azure Repos extension as well as Team Explorer 2019 or Team Explorer Everywhere.
Want to become Azure Developer, check out this Azure Tutorial.
And also check out Intellipaat's Azure Certification and become an Azure expert