mac os x 10.14

What year MacBook Air do you have?

Monterey requires a 2015 or later one.

To get it go to the App store and search for macOS Monterey.

Otherwise see the following for getting older macOS version of of what Macs they are compatible with:

How to get old versions of macOS - Apple Support

Specifically:

Check compatibility

The version of macOS that came with your Mac is the earliest version it can use. For example, if your Mac came with macOS Big Sur, it can't use macOS Catalina or earlier. If a macOS isn't compatible with your device, the App Store or installer will let you know. If you try to install a macOS that is older than the version currently installed, the installer will say that it is too old to be opened on this version of macOS.

• macOS Big Sur 11 hardware requirements
• macOS Catalina 10.15 hardware requirements
• macOS Mojave 10.14 hardware requirements
• macOS High Sierra 10.13 hardware requirements
• macOS Sierra 10.12 hardware requirements
• OS X El Capitan 10.11 hardware requirements
• OS X Yosemite 10.10 hardware requirements

If you are referring to Yosemite updates through the App Store, then what it's tell you is there are no updates at this time. If you are referring to all other downloads, they would be in whatever you set in your web browsers for where to put the downloads. That would be in the web browsers under preferences, downloads. In the App Store at the top you will see Updates and Purchases. If you click on one of them It will display what updates you have downloaded and installed and what purchases you have downloaded or made.