JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-3.4.1.slim.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.css">
<div class="modal" id="galleryModal">
  <div class="modal-dialog modal-dialog-centered modal-dialog-scrollable modal-xl">
    <div class="modal-content">
      <div class="gallery">
        <div class="gallery-item">
          <img src="https://preview.ibb.co/kPE1D6/clouds.jpg">
        </div>
        <div class="gallery-item">
          <img src="https://preview.ibb.co/mwsA6R/img7.jpg">
        </div>
        <div class="gallery-item">
          <img src="https://preview.ibb.co/kZGsLm/img8.jpg">
        </div>
      </div>
    </div>
  </div>
</div>

<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#galleryModal">
Modal
</button>

CSS

.gallery {
  overflow-y: auto !important;
}

.gallery-item {
  margin: 5px;
  float: left;
}

.gallery-item img {
  height: 150px;
  width: 200px;
  object-fit: cover;
}

.btn {
  margin: 5px;
}