You have to try to get something official from the court saying the records are not available. I got an RFE for court records (because my idiot brain thought I could just tell USCIS about the case on my I-129F and not provide documentation 🤪) and this was the verbiage I got in the RFE:
If the court dispositior(s) is/are not available, you must obtain a certified letter from the court(s) stating that there is no record.You may submit original documents establishing the norrexistence of court records, or certified copies which must include the relevant court seal stamps. In addition to evidence establishing the court documents are not available, submit a notarized statement detailing the events that lead to the arrest, the arresting agency, what charges were filed by the arresting agency, the final disposition (guilty, not guilty etc.) of all of the charges with a list of the charges, the location of the court and any punishments.