Yes, you are correct. $6,500 is your non-deductible basis at 12/31/2023 and zero is the basis for 12/31/2024.
Don't forget to enter the 2024 $7,000 non-deductible IRA contribution in the deduction and credits section. This will ensure the $13,500 rollover (except additional interest) will be tax-free.
To review the full steps to report a backdoor Roth in TurboTax Online, see: How do I enter a backdoor Roth IRA conversion?:
