as a sale of the property as if there was no like-kind exchange.  thus cost would be the cost of the latest property reduced by the gains deferred from past 1031's  TT should have this info if 1031's were handled correctly for the prior returns where a 1031 occurred.

To properly report this as Sale of Business property and if you are in Turbo Tax Online, you will need to report this as sale of business property.

Go to federal>wages and income>see all income>other business situations>Sale of Business Property>start
Next screen you will say none of the above You will see an entry there for like-kind exchanges but you will not select that because this current transaction is not a like kind-exchange. Then it will ask you questions about this transactions. Just follow the prompts