Hi!
Make sure that you have downloaded the ‘Installable wordpress plugin’ only when clicking the download button: https://i.imgur.com/PU6tHzo.png
Codecanyon provides a full archive as well, which contains the documentation and screenshots as well, that cannot be installed without extracting it first.
For the full installation details you can check this documentation: https://documentation.ajaxsearchpro.com/installation-instructions
I hope this helps!