Windows 10 version 1903 (May 2019 Update) has officially reached the end of support on December 8, 2020. This applies for all editions of the operating system, including Windows 10 Home, Pro, Enterprise, Education, and even Windows Server version 1903.
Although you can technically continue to use version 1903, since Microsoft no longer offers supports for this release, devices running this version will stop receiving security and quality updates, and you will no longer be able to contact the company for support.
If you have a device still using the May 2019 Update, the system will soon (next couple of weeks and months) upgrade automatically to the next supported version, which in this case will be version 1909 (November 2019 Update). However, you can always upgrade manually to the November 2019 Update or higher release, including version 2004 or 20H2.
To upgrade manually, you should be able to complete the task from Settings > Update & Security > Windows Update, click the Check for updates button, and then clicking the Download and install option for the newer version available on your device.
Once the feature update downloads and install, you will need to restart your computer to apply the changes. The installation process should not take a long time, since version 1909 is a small update with only a few minor improvements and features, and the installation does not require full reinstallation.