If you are reinstalling this specific version, here are the highlights you can expect:
For the vast majority of users searching for a "Windows 10 ISO," the goal is simply a clean install of the operating system. In 99% of cases, downloading the latest Windows 10 ISO (currently version 22H2) is the superior choice. It contains all the improvements of 1903 but with modern security patches, better driver support, and long-term stability.
If the official site only provides the latest version, you can find original, unmodified ISO files on community-driven archives.