The TurboTax system should calculate the gain or loss that you have using the information that you are entering even if your brokerage chose not to calculate that for you. So that part is fine.
If you have trades on your 1099-B that don't have any basis then that may mean that the broker didn't know when you bought those stocks or how much you paid for them. That can happen when you're selling off things that you have had for a long time.
If you aren't sure when you bought them or how much you paid either then it is best to contact the broker who issued you the 1099-B and see if they have any clues that they can offer to help you find the cost basis.
@XXSHNAYXX
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