NJ  is asking about your original traditional IRA contributions (basis) from the past. Since NJ doesn't allow a deduction for traditional IRA contributions (unlike the IRS), the amount of your withdrawal that represents your previously taxed contributions is tax free. If you converted traditional IRA contributions to a  Roth IRA in the past, and you still had balances in your traditional IRAs,  part of the Roth conversion will be non taxable and part will be taxable, and the remaining non-deductible basis would carry forward for future distributions. 

See this  NJ Tax Topic Bulletin concerning traditional IRA contributions and distributions. See page 5 for how to calculate how much of your distribution is tax free in NJ.