Value for Transaction ID of Purchase Order Approval Test Workbench?

Value for Transaction ID of Purchase Order Approval Test Workbench?

All approval related attributes, conditions, groups and rules have been defined for Purchase Order approval.

In order to use the test workbench to test the approval rule the transaction id is required. Therefore, the "PO_HEADER_ID" value from the table PO_HEADERS_ALL was used as the transaction ID in the test workbench. However, the following error occurs.

Please address the following issues,

1. How to rectify the above error?
2. From where can the "Transaction ID" for Purchase Orders be obtained?