You are supposed to figure out the term for unknown term capital gains. It is unknown to the broker managing your account. In theory you are supposed to go to your records, figure out when you bought those shares as well as what you paid for them at that time and enter those numbers into TurboTax.
If you are unable to figure it out because it was so long ago then you can enter long term (because it was more than a year ago) and a basis of zero and you will be safe.
@madmaxusmc