JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent" style="height:180px">
<div class="child">
<header>title</header>
<div>test11</div>
<button>
Test
</button>
<button>
Cancel
</button>
</div>
</div>

CSS

* {
  box-sizing: border-box;
}
.parent {
  max-height: 300px;
  margin: 0 auto;
  background-color: #fff;
  position: fixed;
  top: 20%;
  left: 20%;
  border: 1px solid #000;
  width: 234px;
}
.child {
  padding: 40px 54px 54px;
  display:flex;
  height:100%;
  align-items:center;
  justify-content:center
}