Dear Theron Snell:
Thank you for posting your question on History Hub!
You may wish to consult the FamilySearch Research wiki for Martinique Immigration records.
Unless Grete Stoffel arrived or left the United States, the National Archives would not have relevant records. You can try searching the country of origin. You mentioned Stoffel arrived in Martinique, if you knew where they came from, you could try conducting a search of that country’s records to see if they have departing passenger lists.
If you have not done so already, we suggest that you review NARA’s Resources for Genealogists, as well as the History Hub Blog titled Suggestions and Advice for Family History Researchers. Also, the FamilySearch Research wiki for United States Genealogy may be useful.
We hope this information assists with your research!
I was able to find archival sources elsewhere for Stoffel. Thank you.