It seems you must be using the Zones shipping module.
Edit the zones shipping module.
Around line 120, you see this:
Code:
$dest_country = $order->delivery['country']['iso_code_2'];
Add another line below it, like this:
Code:
$dest_country = $order->delivery['country']['iso_code_2'];
$dest_country3 = $order->delivery['country']['iso_code_3'];
There are 3 ways to configure the module, and thus 3 different places where you could display the 3-char code instead.
Look for these 3 lines, and change $dest_country to $dest_country3 instead:
Line 171:
Code:
$shipping_method = MODULE_SHIPPING_ZONES_TEXT_WAY . ' ' . $dest_country . $show_box_weight;
Line 185:
Code:
$shipping_method = MODULE_SHIPPING_ZONES_TEXT_WAY . ' ' . $dest_country;
Line 199:
Code:
$shipping_method = MODULE_SHIPPING_ZONES_TEXT_WAY . ' ' . $dest_country;