How do I update firefox software in Linux.

You appear to have the current Firefox 151.0 on Linux. https://support.mozilla.org/en-US/kb/install-firefox-linux This is for the official version from Mozilla and not the snap, flatpak, deb, rpm etc versions. https://support.mozilla.org/en-US/kb/update-firefox-latest-release If you use the Linux tarball from Mozilla https://www.firefox.com/download/all/ then you need to make sure the Firefox folder have read/write permissions for the user account on Linux distro to get internal Firefox updates the same way as on Windows and macOS Firefox.