I have a macbook pro from 2013. I can't seem to update my Mac utilizing any software update... What is the best version of Mac OS I can use?

..Big Sur..

• How to get old versions macOS - Apple Support

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

re: "..Safari uses these links to find the old Installers in the App Store.

After you 'download the installer' from the App Store, the Installer opens automatically.."

• macOS Big Sur 11 can upgrade Catalina, Mojave, High Sierra,

Sierra, El Capitan, Yosemite, Mavericks

https://apps.apple.com/us/app/macos-big-sur/id1526878132?mt=12

re: "..Safari uses these links to find the old Installers in the App Store.

After you 'download the installer' from the App Store, the Installer opens automatically.."

• macOS Big Sur 11 can upgrade Catalina, Mojave, High Sierra, Sierra, El Capitan, Yosemite, Mavericks

https://apps.apple.com/us/app/macos-big-sur/id1526878132?mt=12

Could be IF the MacBook Pro actually is older than Late 2013, an even older macOS may work best.

Take care & good luck!🌞🐝

PS:

To OP: avoid command lines. Get the correct installer

download, based on MB/Pro build model. Mojave or

Catalina; & make TM backups before proceeding.

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

Pretty sure it's going to be an app file not a dmg. Been a while since I downloaded a MacOS file.

If you need to create a bootable installation flash drive, I like the free Install Disk Creator app for that.

Big Sur is the latest OS you can use.

"Best" is very subjective. I liked Big Sur and all our Macs did too, but you may not.

If you're looking for 32 bit compatibility, you'll to have to drop back further.

What exactly is you goal or need in trying to upgrade?

From Terminal:

softwareupdate -l

That command will list any updates available (from the Bash shell).

I don’t know -zsh, sorry!