I want to download iTunes for Mac air

What version of macOS are you running, click on the top left of your screen

and click on About This Mac.

iTunes comes as part of the OS there are no standalone downloads for it,

there may be updates available through the App Store Updates page.

If there are no outstanding updates available you are running the latest/ last version

of iTunes for the OS you are running.

If your mac is running macOS Catalina or macOS Big Sur iTunes was dropped

in favour of the Music app.

daman117 wrote:

how can install latest version iTunes in Mac book air

This implies iTunes is not installed on this computer. That would be very not normal unless this computer is running Catalina or Big Sur . If running Catalina or Big Sur - iTunes can not be downloaded and installed.

iTunes was split into three separate applications called Music, Podcasts and TV