JSFiddle - React, Tailwind, and code Playground

HTML

<button id="btn">pew</button>
<div class="block">
  <h2>BLOCK 1</h2>
  <div class="content">my content</div>
  Lorem ipsum
</div>
<div class="block second">
  <h2>BLOCK 2</h2>
</div>

CSS

.block {
  margin: 1em;
  padding: 1em;
  border: solid 2px gray;
}

JavaScript

btn.onclick = function(){
	let content = document.querySelector('.content')
  let target = document.querySelector('.block.second')
  
  target.appendChild(content)
}