Change ID# to SKU Responsive Shop Theme

Could anyone advise how to add sku to the invoice page? This is critical information but is currently missing.

I added the following code as instructed:

SKU:<?php $key_1_value = get_post_meta( get_the_ID(), ‘sku’, true );
// Check if the custom field has a value.
if ( ! empty( $key_1_value ) ) {
echo $key_1_value;
} ?>

?>

<table class=”table table-bordered”>
<thead>
<tr>
<th><h4>Package</h4></th>
<th><h4>Description</h4></th>
<th><h4>Sub Total</h4></th>
</tr>
</thead>
<tbody>
<tr>
<td>
<?php echo $order->order_data; ?>
</td>
<td>ID); ?>”><?php //echo $postdata->post_title; ?>
<?php if(get_post_meta($postdata->ID,’sku’,true) != “”){ echo “(“.get_post_meta($postdata->ID,’sku’,true).”)”; } ?>
<?php if(get_post_meta($postdata->ID,’SKU’,true) != “”){ echo “(“.get_post_meta($postdata->ID,’SKU’,true).”)”; } ?>
</td>
<td class=”text-right”><?php echo hook_price($order->order_total); ?></td>
<td>[code title=””]
<?php $sku_value = get_post_meta( get_the_ID(), ‘sku’, true );
// Check if the custom field has a value.
if ( ! empty( $key_1_value ) ) {
echo $sku_value;
} ?>
[/code]
</td>
</tr>

</tbody>
</table>