Everything about the inherited IRA is separate from your own IRAs.
TurboTax track your own basis in nondeductible traditional IRA contributions on its IRA Information Worksheet. You can look there to see if TurboTax has carried over your basis from your 2017 Form 8606 line 14. Note that you can inadvertently cause TurboTax to silently delete your basis if you mistakenly ever answer No when TurboTax asks if you made nondeductible contributions to your traditional IRAs.
Since the decedent had no basis in nondeductible traditional IRA contributions, the entire distribution that you took from the inherited IRA is taxable. Your own basis does not apply to distributions from the inherited IRA.
