Welcome to the forums, @prateekjadhav25.
I'm sorry, but your post makes no sense. If you buy an expired domain and use it to create a new site, it will be treated as a new site, just as if you'd bought a new domain. You might initially get a boost from any incoming links which have not been removed, but search engines will rapidly detect that these links are no longer relevant. Many links will be broken, as the pages they linked to no longer exist.
Page Authority is a metric created and used by moz.com, and has no bearing on search results. In any case, changing the site will change the PA.
The most important thing for search engine ranking is high-quality, unique content.