Your relatives should go the county or city that you were originally charged for and request the records. You will probably have to sign a release to allow someone else to obtain the records.
If you were in the U.S. unlawfully when you were arrested, the fact that you were not charged may not matter as it would still make you inadmissible. You should consult an immigration attorney to help you with your case and see if there is any form of relief for you to return to the U.S.
Gabriela M. Lopez, Esq.