TurboTax asks separately about regular net contributions and net conversion contributions. However, you don't really need to enter this amount since your distribution is a qualified distribution. The only reason that you would need to know your net contributions and conversions now is if you had sufficient investment losses to be able to claim a miscellaneous deduction for unrecoverable contribution and conversion basis after completely distributing all of your assets from your Roth IRAs, which doesn't seem likely.