I am unable to find popular apps in MacBook Air App Store.

Netflix doesn't make a desktop application. On a Mac, you access Netflix through a web browser.

Unlike the iPad and the iPhone, Macs can download applications from other sources. You are not limited to the App Store. I would suggest, though, that you do your due diligence and make sure that any third-party developer you'r'e getting an app from is reputable.

What happens when you tap App Store -> then tap the 'Search' icon, then type Netflix in the field?

For Plans and Pricing see -> https://help.netflix.com/en/node/24926