Bonjour,
Pour cela la solution sera d'utiliser un champs personnalisé de la table "Commande" et comme indiqué via la documentation des champs personnalisés :
With the order custom fields (business edition only), you will be able to personalize the information you can also gather from your customers when they order something on your store. But the difference with the previous type of custom field is that these fields appear on the checkout in the fields view. For example, You can ask them information about the delivery or the payment or a "comments to the shop" field. Then, you will find this information on the order details and/or the orders listing on the back end.
Une version business sera donc nécessaire pour les utiliser.