prevent post pages indexing in search engines

Hi,

I have a blog called techpopular.com, in this my blog like previous post numbers are also indexed, i’m not sure how to prevent it. In my sitemap it never shows i,e for eg :techpopular.com/page/3/‎. how to avoid them, recently i added a plugin to edit my robot.txt. Can you please tell me what is the issue and how to solve it.