Mail to: Dallas County Sheriff's Dept. , 133 N. Riverfront Blvd.F) Print the confirmation document, sign the authorization letter and fill in the contact information. 3. Please complete the U Visa Request Form. Get an "Application for Naturalization" (Form N-400). What type of immigration case do you have or what agency are you submitting this "police clearance" evidence to? Police officers killed in the lineofduty.