Perhaps if you know the present version & step of macOS now installed
on your Mac's drive ~ that may help to determine what might be next.
From what I could tell from reference MacTracker &/or Everymac site
the model year would have shipped with version macOS Sierra 10.12.4.
(Could be a newer version macOS may need installed; before the last
supported version may be allowed to be installed. Happened before.)
MacBook Air (13-inch, 2017)
Introduced June 2017 - Discontinued July 2019
Model Identifier MacBookAir7,2 - Model NumberA1466
EMC3178 - Order Number(s) MQD32LL/A (128 GB storage), or MQD42LL/A (256 GB storage)
Further upgrades would be downloadable installers that then would
be run from within your Mac to do just that; before they'd be able to
run a Mac... they'd need to fully download parts and install them all.
See compatible versions and how to download (use Safari).
• How to get old versions of macOS - Apple Support
https://support.apple.com/en-us/HT211683
Could take a few hours, and several re-starts.
Plus additional downloads.
"..Before installing any upgrade, it’s a good idea to back up your Mac. (link)
Time Machine makes it simple, & other backup methods are also available."
Good luck & happy trails! ☺︎