When you sell a noncovered security, the cost basis does NOT have to be reported on the 1099B Form. If you received any paperwork along with the 1099B Form, sometimes the cost basis and purchase date will be included in that paperwork. If it is NOT included in that paperwork, then you need to look through the investment paperwork that you have to try to determine the time frame in which you purchased the stock. Once you establish a time frame, you can look up historical prices on the internet in order to identify the cost basis.
This is an FAQ that provides additional information for how to determine when you purchased the stock. https://ttlc.intuit.com/replies/5393232
With respect to box 1b for acquisition date, if you cant determine the actual date, then you can type in the word, various, in the box where you would normally type in the date.