The APIF, APDF, APTXF record types are used for the Fixed import format which stays static. Refer to What is the AP Import Invoices Fixed Format?
What information should I include in my Accounts Payable invoice import file?
How do I import invoices into Accounts Payable?
What are the guidelines for Importing Accounts Payable Invoices?
How do I import an invoice with more than one distribution in Accounts Payable?