Microsoft released Windows 10 Build 2004 aka May 2020 update at the end of May 2020. It is supposed to be rolled out to Windows 10 machines in a phased manner. I have seen some machines where Build 2004 has not shown up as an update option as of this writing in September 2020. This does not mean that you can not update your Windows 10 machine to this new build. You will have to install this update manually.
You can go to Download Windows 10 page on Microsoft Website. Click on Update Now button. It will download installer on your machine. Click on the installer on and follow the steps. The installer will first check if your machine is ready for update or not to make sure that your hardware meets the requirements. This update will take place in the background. You can continue working on your tasks till its time to complete the update process.