I cannot find the App Store on my MacBook Air 2019

The App Store application is pre-installed. It has an icon that looks like this:

If you don't see it in the Dock, try looking in the Applications folder, or using Spotlight to search for "App Store."

In the very unlikely event that you have deleted the App Store application – not merely misplaced it – the only way to get it back might be by reinstalling macOS.

The Mac App Store originally appeared in Mac OS X 10.6.8 (Snow Leopard), and at some point there was a patch that you could download to let Snow Leopard stay compatible with then-newer versions of the App Store. I don't ever recall seeing any sort of standalone download for the full App Store application, probably because none was ever needed.

If you cannot find the App Store on your Mac:

The App Store can't be permanently deleted, but it can be restricted through Screen Time settings. Here's how to check if it's disabled and enable it again:

1. Go to Settings.
2. Tap on Screen Time.
3. Select Content & Privacy Restrictions.
4. Look for Store Restrictions.
5. Make sure all the toggles under iTunes & App Store Purchases are turned ON (blue).

Or disable Restrictions altogether by toggling the switch off

Can't find the App Store? It might be disabled!

The App Store can't be permanently deleted, but it can be restricted through Screen Time settings. Here's how to check if it's disabled and enable it again:

1. Go to Settings.
2. Tap on Screen Time.
3. Select Content & Privacy Restrictions.
4. Look for Store Restrictions.
5. Make sure all the toggles under iTunes & App Store Purchases are turned ON (blue).

Or disable Restrictions altogether by toggling the switch off