In order to settle the payment at the convenience store, you do NOT need the physical Smartpit card.
Kindly be assured you can find your Smartpit number via the [Sakura Mobile My Page].
If it's your first time to log-in on the My page website, kindly refer to this article on How to log in to [Sakura Mobile My Page] for the first time?
1- After you log in to your page, kindly click on the three dots on the upper right as shown in the below picture:
2- From the menu, please click on (Account)
3- From the Account page, you can see your personal information, as well as the Smartpit number.
Kindly note you can NOT use 7/11 convenience stores to pay the bill. Thank you for understanding.