You do not state whether these were iWork '08, iWork '09, or newer, replacement applications. You do not state what version of OS X, or macOS was on the MacBook Air before you wiped it, or afterward (though I surmise High Sierra 10.13.6). Important information.
As macOS High Sierra (10.13.6) is the last operating system supported on that Mid-2011 MacBook Air, you would need to be able to obtain Pages v7.3 through v8.1, Numbers v5.3 through v6.1, and Keynote v8.3 through 9.1 from a Time Machine restore, or by attempting the third paragraph approach. Older, or newer versions of these applications than stated here will not work on High Sierra 10.13.6.
You can try the Mac App Store using the option key while clicking on the Purchases tab. If Pages, Numbers, and Keynote are listed, you may have the option of obtaining them again. There is a possibility that the Mac App Store will install the latest version of the mentioned applications compatible with High Sierra — or nothing. If this fails, then know that Apple does not otherwise, maintain full, past installers of these applications for download.
If Time Machine restore, and Mac App Store approaches fail, then you are done with these applications on High Sierra, short of using their iCloud versions.