Enter them all so that TurboTax will correctly track your basis going forward and will correctly calculate the taxable amounts of future distributions. If the oldest conversion was in 2017 or later and you have not yet reached age 59½, that conversion will not yet have completed the 5-year conversion holding period and the portion of that conversion that was taxable upon conversion will be subject to a recapture of the 10% early-distribution penalty.
If you've already distributed some amount of your conversion basis, you'll need to adjust the amounts that you enter into TurboTax as your conversion basis. Only enter into 2020 TurboTax the amounts of basis that remained in your Roth IRAs at the beginning of 2020.
TurboTax tracks your Roth IRA contribution and conversion basis on its IRA Information Worksheet.
