For modern versions of Windows (10 and 11), you typically do not need to download a separate installer; it is built-in and can be enabled through your system settings. Official Download Links
Understanding .NET Framework 3.5: Your All-in-One Compatibility Solution net framework 35 includes net 20 and 30 download link
Understanding .NET Framework 3.5: Why It Includes 2.0 and 3.0 (and Where to Download) For modern versions of Windows (10 and 11),