how to update my safari

Check the computer requirements shown in each link to see if your computer is capable of running that OS version.

macOS Big Sur is compatible with these computers

Catalina

How to upgrade to macOS Mojave - Apple Support

How to get macOS High Sierra   

Sierra download

Check to make sure your applications are compatible.      

Application Compatibility

macOS Sierra 10.12: Compatible Apps

Also check to make sure there is a compatible driver for your printer.

Do a backup before installing, preferable 2 backups on 2 different drives.

Click in the menu bar.

Do you see App Store?

If yes, App Store > Updates

Quote:

Updating Safari

To keep Safari up to date for the version of macOS you're using, install the latest macOS updates.

The most recent version of macOS includes the most recent version of Safari. For some earlier versions of macOS, Safari might also be available separately from the Updates tab of the App Store.

https://support.apple.com/en-us/HT204416