1099-B Enter Adjust Cost Basis

Nothing is really clear on TurboTax or my prior employer's employee stock plan. All I received is a 1099-B because I cashed out of that old plan. I can enter most of the information requested from TurboTax but the Adjusted Cost Basis. TurboTax only had 8-line items of 50 for me to review. Not sure if, that is correct as many other line items appear to need adjustment. The advice provided by TurboTax in the following is not helpful for me:

"You can find your adjusted cost basis on a supplemental form provided by your financial institution. It’s usually available by mid-February along with Form 1099-B.

If you can’t find a supplemental form, we can use Form 3922 to determine your adjusted cost basis for each stock sale. We’ll need it for the year you originally purchased the ESPP stock you sold."