I need to upgrade my macbookair laptop

Start here: How to get old versions of macOS - Apple Support

There's a link there to the current Monterey, if your Mac supports that.

Have a backup prior to the upgrade.

If you upgrade to 10.15 or later—if your MacBook Air supports that—you will want to ensure all of your apps are 64-bit. This includes printer and scanner drivers. Existing 32-bit apps will need to be updated, upgraded, retired, or replaced. Office 2011 and earlier, for instance, are 32-bit apps, and will not work with 10.15 and later. For a tool useful in finding these older 32-bit apps, the Go64 tool works.

13GrandKids! Said:

"I need to upgrade my macbookair laptop: how to upgrade my macbook air it is an older version"

-------

Updating the macOS:

Determining which Update(s) will Install:

I. Verify Compatibility:

A. Start Here: Learn About Compatibility and how to Identify your Specific Mac Model - Apple Support

B. How to Verify:

I Reveal your Model:

What is the Model of your Mac? To find out...

1. Go to: Apple menu
2. Click: About this Mac
3. View: Second Line-Down

then...

II. Compare the Results:

See if the Model you found is shown here:

• macOS Monterey is Compatible with these Computers - Apple Support
• macOS Big Sur 11 Hardware Requirements - Apple Support
• macOS Catalina 10.15 - Hardware Requirements - Apple Support
• macOS Mojave 10.14 - Hardware Requirements - Apple Support
• macOS High Sierra 10.13 - Hardware Requirements - Apple Support
• macOS Sierra 10.12 - Hardware Requirements - Apple Support
• OS X El Capitan 10.11 - Hardware Requirements - Apple Support
• OS X Yosemite 10.10 - Hardware Requirements - Apple Support

III. If Compatible:

Back Up your Mac First:  Be certain you Create a Time Machine Backup of your Mac, so that way you can have something to restore your Mac from, should anything go wrong with the reconfiguration.