<div class="container">
  <div class="item">1</div>
  <div class="item">2</div>
  <div class="item">3</div>
  <div class="item">4</div>
  <div class="item">5</div>
  <div class="item">6</div>
</div>
.container {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 15px;
}

.item {
  background: #e3f2fd;
  padding: 20px;
  text-align: center;
  border-radius: 8px;
}