Changing internal post page content

Hello,

I have what seems to be a very simple issue, but cannot seem to locate this myself. I have been customising my wordpress theme, by changing the page.php and page-blog.php files to edit the blog/news page of my site.

But now I am trying to edit the individual news/blog post page, but cannot seem to locate the correct php file in my theme.

What is the common location or file name for this file, or id this an individual file?

Thank you for your help,

James.