<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/css/bootstrap.min.css" rel="stylesheet">
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/js/bootstrap.bundle.min.js"></script>

<div class="container">
  <div class="row g-4">
    <div class="col-12 col-md-6 col-lg-4">Card 1</div>
    <div class="col-12 col-md-6 col-lg-4">Card 2</div>
    <div class="col-12 col-md-12 col-lg-4">Card 3</div>
  </div>
</div>

12 columns; breakpoints sm 576, md 768, lg 992, xl 1200, xxl 1400. Classes apply from that size up (mobile first). g-4 sets gutters.