Will I have to pay an Expected Return on Contract amount if it took money from my 401k as a NJ resident?

Not at all.  The expected return on contract is not something you pay.  It's an amount you are expecting to receive over the life of the retirement plan and its used to determine how much of your distribution is taxable in the state.

Does this amount need to be calculated for any nj resident that took an early withdrawal from their 401k?

How do I calculate the "expected return on contract" ?

the whole concept does not apply to 401k. Just ignore those questions.

I am totally confused about this.  What   do I have to enter in this field to finish my NJ tax return?  I have never seen this field before.