The IDs of the files you want to update the owners of.
To get the file_id, open the file in the SafetyCulture web app and copy the last part of the URL.
For example, in this link https://app.safetyculture.com/documents/document/765aa2e6-69cb-43b5-8ab4-48ab26e2a094,
the file ID is 765aa2e6-69cb-43b5-8ab4-48ab26e2a094.