"Your NJ IRA basis is your total traditional IRA contributions."
For purposes of the first year calculation, your NJ IRA basis is your total traditional IRA contributions, less any amounts you already distributed but did not pay NJ tax on.
You will need good records showing what you put in over the years, or some way to reconstruct that information.
Since a Roth IRA is generally not taxable, there is nothing to be recovered.
