Bootstrap CSS class .justify-content-md-center

    <div class="d-flex flex-wrap justify-content-md-center bg-secondary" style="height: 50px;">
        <div class="px-4 bg-primary"></div>
        <div class="px-4 bg-info"></div>
        <div class="px-4 bg-primary"></div>
        <div class="px-4 bg-info"></div>
        <div class="px-4 bg-primary"></div>
        <div class="px-4 bg-info"></div>
    </div>