If you properly prepared your 2017 Form 8606, line 14 of the 2017 Form 8606 would have $5,500 that would transfer to line 2 of your 2018 Form 8606. The separate $5,500 on line 1 of your 2018 Form 8606 would be added to that, resulting in line 14 of your 2018 Form 8606 having $11,000. The $11,000 from line 14 of your 2018 Form 8606 will transfer to line 2 of your 2019 Form 8606 to be used to determine the taxable amount of your 2019 Roth conversion.
If 2018 TurboTax is not showing the $5,500 on line 2 of the Form 8606, revisit the Traditional IRA contribution section, answer Yes, you made and tracked nondeductible contributions to your IRA, then enter your $5,500 of basis carried into 2018 from 2017 (the amount shown on line 14 of your 2017 Form 8606).
