You should contact the appropriate courts or police departments to get copies of the records. Some courts may require you to pay a fee to conduct a records search or make copies of records. You are responsible for paying those fees.
In some cases, the courts (and, less frequently, the police departments) will not have copies of the records because of the length of time since the case. In particular, most courts will purge records a certain number of years after the case is closed. You should ask the court for a statement that it searched its records but could not locate a case. This statement will show either that you were not convicted of the offense in that court or that you completed any sentencing requirements because a court will not purge records unless the case was closed.
For more information about the requirement to submit court documents, please download our guide on court documents.