Add serial field to admin - WordPress

functions.php

<?php 

add_filter('manage_edit-shop_order_columns', 'edit_shop_order_columns');
function edit_shop_order_columns($columns)
{
    $columns = array(
        'cb' => '&lt;input type="checkbox" />',
        'order_number' => __('Order') ,
        'order_date' => __('Order Date') ,
        'order_status' => __('Status') ,
        'serial' => __('Serial Number') ,
        'order_total' => __('Order Total') ,
    );
    return $columns;
}
add_action('manage_shop_order_posts_custom_column', 'shop_order_column', 10, 2);

function shop_order_column($column, $post_id)
{
    global $post;
    $arr = "";
    if ('serial' === $column)
    {
        echo get_field('order_serial_number', $post_id);
    }
}

add_filter('manage_edit-serialnumber_columns', 'edit_serialnumber_columns');
function edit_serialnumber_columns($columns)
{

    $columns = array(
        'cb' => '&lt;input type="checkbox" />',
        'title' => __('Serial Numner') ,
        'products' => __('Linked Products') ,
        'SKU' => __('SKU') ,
        'status' => __('Status') ,
        'date' => __('Added Date')
    );

    return $columns;
}

add_action('manage_serialnumber_posts_custom_column', 'realestate_column', 10, 2);
function realestate_column($column, $post_id)
{
    global $post;
    $arr = "";
    if ('products' === $column)
    {
        $productlist = get_field('products', $post_id);
        foreach ($productlist as $row)
        {
            $arr[] = get_the_title($row);
        }
        echo implode(",", $arr);
    }
    $sku = "";
    if ('SKU' === $column)
    {
        $productlist = get_field('products', $post_id);
        foreach ($productlist as $row)
        {
            $product = wc_get_product($row);
            echo $row;
            $sku[] = $product->get_sku();
        }
        echo implode(",", $sku);
    }

    if ('status' === $column)
    {
        echo get_field('available', $post_id);
    }

}