If the court granted you probation, and you successfully completed that probation, then you will likely qualify to expunge the criminal case at the end of the period of probation.
Successful completion of probation means that you (1) served the time on probation, (2) paid all your fines and restitution, (3) attended your court dates, (4) didn’t commit any new crimes, (5) and completed any conditions of probation that the court imposed (such as CALTRANS, community service or counseling).
You should contact an attorney to ensure that the documents are prepared and filed properly and to handle any objections from the district attorney or judge.
Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.
You must successfully complete probation for the entire period of probation. Fill out a petition for expungement and file it with the court and serve the prosecutor. A fee is usually required to file the petition. You may need the help of a lawyer when doing this. Good luck.