I am having trouble updating my macbook

Is there a misunderstanding with page content here?

• How to update the software on your Mac - Apple Support

https://support.apple.com/en-us/HT201541

First things would need to be shared for better grasp.

• About System Information on your Mac - Apple Support

https://support.apple.com/en-us/HT203001

Choose Apple menu  > About This Mac. "This opens an overview of your Mac,

including your Mac model, processor, memory, serial number, and version of mac

OS. ~ To see the greater detail provided by the System Information app, click the

System Report button."

No need to share a serial number; those get removed

from the posts anyway. Not helpful. Identify your Mac:

• Lookup Mac Specs @ everymac.com

https://everymac.com/ultimate-mac-lookup/

Your MacBook Air may have no further up-date in

an already outdated older macOS version. Could

be better idea: Check for an Upgrade, a higher level.

Depending on the vintage or build version of your

model year MacBook Air (or any other Mac) options

may not include support of latest most recent macOS.

An older macOS may be better suited. See those here:

• How to get old versions of macOS - Apple Support

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

• macOS11.x Big Sur is compatible with these computers - Apple Support

https://support.apple.com/en-us/HT211238

• macOS Monterey - Wikipedia (just announced)

https://en.wikipedia.org/wiki/MacOS_Monterey

By sharing the details of your Mac, there are databases

online to discover widely known & published answers.

Everymac.com site has most info online. Consider the

free Mactracker download/database app, to use offline.