Kalispell Municipal Court does not have the power to expunge a conviction. The legislature has granted that authority exclusively to District Courts.
If your sentence was deferred at the time it was pronounced AND you have successfully completed all conditions of the sentence, the Court can dismiss the charge and seal your cause number. What that means is that the public does not have access to the details of the conviction and your criminal record will state that the charge has been dismissed.
If you believe you meet both of these conditions, then you should file a Motion to Dismiss with the court.
This request will be denied if the Court finds that you (1) did not complete all conditions of your sentence on time; (2) if you had a new charge during the time the deferred sentence was running or (3) if the time for deferment has not expired.
If you did not receive a deferred sentence and believe your conviction should be taken off your record, you may be best served by consulting an attorney.