Punchh only shows menu item ID's for items that have been sent over to us transactionally from the POS.
In order to see an exclusive list of all menu item ID's for your items, you'll want to access the respective platform for the POS you are using. From there you should be able to export the list of menu item ID's.
If further assistance is required, submit a ticket to Punchh Support. (For help submitting a ticket, click here)