Change title post in Blogspot from H3 to H1

Step 1: Go to your Template select Edit HTML.
Step 2:  Select Blog1 from drop down list Jump to widget.
Step 3: Find <b:includable id='post' var='post'> and select expand.
Step 4: Find

<h3 class='post-title entry-title' itemprop='name'>
      <b:if cond='data:post.link'>
        <a expr:href='data:post.link'><data:post.title/></a>
      <b:else/>
        <b:if cond='data:post.url'>
          <b:if cond='data:blog.url != data:post.url'>
            <a expr:href='data:post.url'><data:post.title/></a>
          <b:else/>
            <data:post.title/>
          </b:if>
        <b:else/>
          <data:post.title/>
        </b:if>
      </b:if>
      </h3>

 Step 5: Replace

<h1 class='post-title entry-title' itemprop='name'>
      <b:if cond='data:post.link'>
        <a expr:href='data:post.link'><data:post.title/></a>
      <b:else/>
        <b:if cond='data:post.url'>
          <b:if cond='data:blog.url != data:post.url'>
            <a expr:href='data:post.url'><data:post.title/></a>
          <b:else/>
            <data:post.title/>
          </b:if>
        <b:else/>
          <data:post.title/>
        </b:if>
      </b:if>
      </h1>

Step 6: Finish -> Good luck !