<div class="container">
  <div class="item item--1">
    Item 1
  </div>
  <div class="item item--2">
    Item 2
  </div>
  <div class="item item--3">
    Item 3
  </div>  
  <div class="item item--4">
    Item 4
  </div>    
</div>

.item.item--3 {
  order: 1;
  font-weight: bold;
  background-color: darkgrey;
}

/* ETC (Formatting only): */

body {
  margin: 1.5em;
  font-size: 130%;
  font-family: sans-serif;
}

.container {
  border: 5px solid black;
  display: flex;
  gap: 1em;
  padding: 1em;
}

.item {  
  flex: 1;
  padding: 1em;
  text-align: center;
  background: lightgrey;
  border-color: black;
  height: 5em;
  min-width: 5em;
  border: 2px solid grey;
}