For applicants who are currently holding B-2 status and are seeking to extend their stay, USCIS stresses out the importance of submitting the following documents as initial evidence:
• The original I-94, Arrival-Departure Record, or a front and back copy;
• A copy of applicant's passport; and
• A statement explaining why the applicant is requesting an extension of stay in the United States.
USCIS – Information on Filing Form I-539
Information on Filing Form I-539. USCIS reminds applicants to include all required evidence when submitting Form I-539, Application to Extend/Change Nonimmigrant Status. The required initial evidence for nonimmigrants requesting an extension of stay is included in the instructions for Form I-539 …