This is not a regular traditional IRA contribution. Remove the related entry that you made under Deductions & Credits. Enter the rollover only by entering the Form 1099-R that reports the distribution from the 401(k), nowhere else, and answer the questions that TurboTax asks for this 1099-R.
Separately, enter the Form 1099-R that reports the distribution from the traditional IRA and indicate that you converted the entire distribution to Roth. TurboTax will prepare Form 8606 to calculate the taxable amount.
The Form 1099-R from the 401(k) is the one without the IRA/SEP/SIMPLE box marked. The Form 1099-R from the traditional IRA is the one that has the IRA/SEP/SIMPLE box marked.
