JSFiddle - React, Tailwind, and code Playground

HTML

<div class="some">1</div>
<div class="some">2</div>
<div class="some">3</div>
<div class="some">4</div>
<div class="some">5</div>
<div class="some">6</div>

JavaScript

var d = document.getElementsByClassName('some')[3].innerHTML = '<div>Нужное содержимое</div>';