Retirement tax questions

Tom, Thanks for the response!  This stock, EMC, was acquired in 2000 with a different brokerage firm.  It had a number of corporate actions, evolving from EMC to DELL DVMT, then to DELL C in 2018.  I received a 2024 1099-B from the current brokerage firm to "conclude" that 2018 corporate action(Wow! you can go back that long!).  The cost basis was not tracked by the original brokerage and hence not reported to IRS. This 1099-B stated that I have a cash payment resulting from the 2018 corporate action.  I assume that this cash payment is a   long term capital gain with no cost basis. I actually found out how I can select the "long term not reported to IRS" option.  So, I'm fine with that.  However, Turbotax insisted to have a value in Box 1b, the acquire date.  But, it's blank in my 1099-B. What is the acquire date I should fill in?  The EMC acquire date or the DELL C conversion date? Thanks for the help!