Surname Issue in Passport

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I have surname issue in my passport Given name in my passport is ABCD XYZ and surname field is blank, now I have to fill a form given by my employer for H1 Visa which I have to submit today EOD, can you let me know how should i fill it in form form says fill in as per the passport. form has three fields First name, middle name and last name, let me know how should I break ABCD XYZ as i'll also get it corrected after filing the petition. Please reply soon as I have to give that form EOD, and let me know after correcting the passport how i can ammend my Visa petition.

TIA for your quick response.

Regards
Parvesh Kumar