modal.css

.modal {
  position: fixed;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  z-index: 100;

  .bg {
    position: absolute;
    background: rgba(0, 0, 0, 0.8);
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
  }

  .content {
    position: absolute;
    top: 0;
    left: 0;
    z-index: 50;
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;

    .inner {
      width: 200px;
      height: 200px;
      background: white;
    }
  }

  .qrcode, .code {
    margin-left: auto;
    margin-right: auto;
  }

  .qrcode {
    width: 70%;
    height: 70%;
    background: gray;
    margin-top: 20px;
  }

  .code {
    margin-top: 10px;
    text-align: center;
  }
}

    <div class="modal">
      <div class="bg"></div>
      <div class="content"> 
        <div class="inner">
          <div class="qrcode"></div>
          <div class="code">0005 2211 89</div>
        </div>
      </div>
    </div>