You have macOS 10.13.6. The application requires macOS 10.15 or later.

Hello. My macbook air early 2014 13 inc' is not accepting apps such as zoom or messenger from safari online downloads, because of these. "You have macOS 10.13.6. The application requires macOS 10.15 or later". Now i checked, app store and theres no notification for updates. What should i do po? Please help me. I am currently needing zoom app and messenger po