Depending on how the judge decides to handle it, it may never make it on a record at all.
Please note that my answering this question, does not in any way mean I represent you for this, or any other case. You need to seek that actual face-to-face advise of any attorney in your area who can advise you further as to your rights.
Your record does NOT automatically get cleared just because you turned 18.
Any criminal conviction will remain on your record forever.
You need to take this case seriously, get an attorney to negotiate this case to avoid a conviction.