JSFiddle - React, Tailwind, and code Playground

HTML

<div class='order'>
    
    <div class='address'>
        <strong>Your order will be shipped to:</strong><br>
        Simon</br>
        123 Main St<br>
        Anytown, CA, US
    </div>
        
    <div class='order-details'>
        Item 1<br>
        Item 2<br>
        Item 3<br>
        Item 4<br>
        Item 5<br>
        Item 6<br>
        Item 7<br>
        Item 8<br>
        Item 9<br>
        Item 10<br>
    </div>
    
    <div class='options'>
        <button>Edit</button>
        <button>Save</button>
    </div>
</div>

CSS

.order
{
    border: 1px solid steelblue;
    margin: 1em;
}

.address 
{
    padding: .5em;
    background: lightsteelblue;
    float: left;
    
    /* this margin does take effect */
    margin-bottom: 1em;
}

.order-details
{
    padding: .5em;
    background: lightsteelblue;
    
    float: left;
    margin-left: 1em;
    
    /* this margin does take effect */
    margin-bottom: 1em;
}

.options
{
    clear: both;
    padding: .5em;
    background: lightyellow;
    
    
    /* this margin only takes effect if it is greater than the height of all the floated items */
    /* try setting it to 20em */
    margin-top: 10em;
}