The reference to non-deductible IRA contributions refers to contributions to a traditional IRA that were designated to be non-deductible. You should answer "yes" to the question about making and tracking non-deductible IRA contributions, since you did that to consummate the backdoor ROTH IRA. You need to indicate that your prior year ending traditional IRA basis at December 31, 2020 was $0, since you converted all of your non-deductible contribution to the ROTH IRA, so there was nothing left in your traditional IRA at December 31, 2020.
You don't need to track previous year IRA non-deductible contributions since they are now in the ROTH IRA, so you don't have any basis (non-deductible contributions) to track anymore. You may need to track the ROTH IRA contributions, however, in the case that you make a premature distribution you would need to know the basis to determine taxable income on earnings.
@NotoriousBOG
[Edited 2/22/2022 at 10:33 AM PST]
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