Since you are under age 59½, the fact that you've met the 5-year holding period is irrelevant unless you are disabled or have used the money for a first-home purchase. If you are not disabled or using the money for a first-home purchase, the taxable amount of your distribution is determined on Part III of For 8606 by applying your basis in Roth IRA contributions and conversion. Be sure to click the Continue button on the Your 1099-R Entries page and tell TurboTax your basis in Roth contributions for years prior to 2018 and your basis in Roth conversion for years prior to 2018.
