You have to add the TC field in the "Part" paragraph. You can use Ctrl+F9 to add the field delimiters, { }, and then type in the code.

To avoid duplicates in the TOC, you must use some other style than Heading 1 for the "Parts"; be sure to customize the style so that its "Outline level" is "Body Text."

My example document should give you an idea on how to do this. Just use the ¶ button to see hidden text such as the TC fields (and other nonprinting marks) and Alt+F9 to see the TOC field (as well as other fields).

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional