JSFiddle - React, Tailwind, and code Playground

HTML

<div class="block">
  <ul class="menu">
    <li>test</li>
    <li>test</li>
    <li>test</li>
    <li class="number">34 3424</li>
    <li class="register">register</li>
    
  </ul>
</div>

CSS

.menu {
  display: flex;
  height: 50px;
  background: #ccc;
  align-items: center;
  justify-content: center;
}

ul {
  list-style: none;
}
li {
  flex-grow:1;
  margin-right: 10px;
}
.number,.register{
  flex-grow:0;
}