Dear Robert Milbourn,
Thank you for posting your question on History Hub!
The information you're seeking would most likely be in Record Group 389 (Records of the Office of the Provost Marshal General 1941- 1975). Information on these records can be found here: https://www.archives.gov/research/guide-fed-records/groups/389.html . After 1943, The Office of the Provost Marshall was tasked with operating POW camps in the United States to house enemy combatants.
For more information on these records, you may contact the Textual Reference Branch at The National Archives at College Park here: email@example.com.
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We hope this information is helpful and best of luck with your research!