Is a conviction of truancy I received as a minor cleared when I turn eighteen?

You probably were not convicted of truancy but instead given deferred disposition which is like probation but at the end of the probationary period after you have completed all the requirements, including community service and payment of fines and fees, the case is dismissed. You will need to check with the court in which the case was prosecuted to be certain of the actual final disposition. If instead you were actually convicted of the offense (which I highly doubt), then the conviction remains on your record. However, it is a class C misdemeanor which is equivalent to a traffic citation. Be certain that the question you are answering does not limit the offenses you must report to those which could result in jail time or are a Class B or higher offense.