Hi

Firefox is currently not available for that operating system. Please appreciate that Microsoft stopped supporting it with updates for most people over ten years ago.

I would strongly recommend that you consider using a more recent version of Windows 10 or 11, or failing that, consider moving to a Linux distribution.

I think the last version of Firefox for Windows Vista was 52.9.0esr, released on June 26, 2018. It's definitely not recommended to run such an old version on the internet for security reasons. (Note: there was a 32-bit version, but not a 64-bit version of Firefox for Vista.) For more information about ancient releases, see: Install an older version of Firefox.

(Note: there was a 32-bit version, but not a 64-bit version of Firefox for Vista.)

Yes the 64-bit or Win64 version of Firefox required Windows 7 or later to run even if you had 64-bit Windows XP or Vista.

The rather old (32-bit) Firefox 52.9.0esr was the latest to support the then EOL Windows XP and Vista. https://support.mozilla.org/en-US/kb/end-support-windows-xp-and-vista

If your Windows Vista system has a 64-bit CPU then you have more options with Linux distros compared to a 32-bit CPU. I do suggest using a lighter desktop environment like XFCE vs say the heavy Gnome and KDE.