Where is the file for customizing navbar and page-header?

Dear community members,
I want to move the breadcrumbs from navbar to page-header (on desk/system view).
I look around the files but can’t find the correct file for page-header.

From base.html I found this:

{% include "templates/includes/navbar/navbar.html" %}

and in navbar.html I found this:

<ul class="nav navbar-nav" id="navbar-breadcrumbs">

I believe these codes must be moved to the page-header html file. But where is it?

Thanks for any help.

I found page.html in templates.
But the code about I put in this file doesn’t show up.
Is there any other things should be done?