How to change h2 class=”entry-title” in inner pages (not the home page)

Hello, I need to change the attribute <h2 <span class="html-attribute-name">class</span>="<span class="html-attribute-value">entry-title</span>"> in inner pages, corresponding to the page title displayed in the middle of the header image. I need to replace it with <h1 <span class="html-attribute-name">class</span>="<span class="html-attribute-value">entry-title</span>"> which is what already happens in the home page. I searched in all php files of the theme but couldn't find a solution, can you please let me know which file I should edit? Many thanks for you help.