Html 引导：将卡放在旋转木马内的中心

我想在旋转木马里用一张卡。但是，我不明白如何将卡片元素放在旋转木马的中心

以下是我到目前为止的情况：

<div class="container">
    <div class="row">
        <div class="col-sm-12">

            <div id="carouselExampleIndicators" class="carousel slide" data-ride="carousel">
                <ol class="carousel-indicators">
                    <li data-target="#carouselExampleIndicators" data-slide-to="0" class="active"></li>
                    <li data-target="#carouselExampleIndicators" data-slide-to="1"></li>
                    <li data-target="#carouselExampleIndicators" data-slide-to="2"></li>
                </ol>
                <div class="carousel-inner text-center">
                    <div class="carousel-item active">
                        <div class="col-md-6 d-flex justify-content-center">
                            <div class="card">
                                <div class="card-body">
                                    <h5 class="card-title">ID</h5>
                                    <input type="number" class="form-control" placeholder="0000" aria-label="Chain ID"
                                        aria-describedby="basic-addon1">
                                    <a routerLink="eth" class="btn btn-primary">Get Started</a>
                                </div>
                            </div>
                        </div>

                    </div>
                    <div class="carousel-item">
                        <p>2</p>
                    </div>
                    <div class="carousel-item">
                        <p>3</p>
                    </div>
                </div>
                <a class="carousel-control-prev" href="#carouselExampleIndicators" role="button" data-slide="prev">
                    <span class="carousel-control-prev-icon" aria-hidden="true"></span>
                    <span class="sr-only">Previous</span>
                </a>
                <a class="carousel-control-next" href="#carouselExampleIndicators" role="button" data-slide="next">
                    <span class="carousel-control-next-icon" aria-hidden="true"></span>
                    <span class="sr-only">Next</span>
                </a>
            </div>
        </div>
    </div>
</div>

身份证件

但我得出以下结论：

如何更改代码，使卡位于旋转木马的中心

其他

更改HTML格式

<div class="carousel-item active">
                        <div class="row d-flex justify-content-center"> <!-- Add Class & Remove Class -->
                          <div class="col-md-6"><!-- Add here Div -->
                            <div class="card">
                                <div class="card-body">
                                    <h5 class="card-title">ID</h5>
                                    <input type="number" class="form-control" placeholder="0000" aria-label="Chain ID"
                                        aria-describedby="basic-addon1">
                                    <a routerLink="eth" class="btn btn-primary">Get Started</a>
                                    </div> <!-- Add div close here -->
                                </div>
                            </div>
                        </div>

                </div>

身份证件