noun
reference number; order number; tracking number
A number used to identify a specific inquiry, order, or shipment when contacting customer service or checking status.
お問い合わせの際は、問い合わせ番号をお知らせください。
Please provide the reference number when making an inquiry.
この問い合わせ番号で配送状況を確認できます。
You can check the delivery status with this tracking number.
Compound of 問い合わせ (inquiry) + 番号 (number).