how do I download current updates

If you aren't showing any updates available under the Apple logo menu you are probably referring to macOS version "upgrades" (like Mojave 10.14, Catalina 10.15, etc.)

You can use the links there to upgrade to a newer macOS:

https://support.apple.com/en-us/HT211683

What you should upgrade to really depends on what software you run, and which version of macOS you are currently running. What you can upgrade to also depends on your current hardware physically.

As #rcosta887 has mentioned. As for upGrades - the Age of the Computer will govern that new version of macOS can be installed. Follow the link in @ rcosta887 posting and verify is your computer qualifies or an UpGRADE and to what version.

Whatever upgrade is decided upon - make a Time Machine Backup before attempting.