On what line do you find your federal gross income?

Your 2019 adjusted gross income (AGI) is on page 1 of your 1040, line 8b. 

Is Federal Gross income the same as the AGI?

"Federal Gross Income" is not a standard tax term. Where do you see that term? Who is asking you for your Federal Gross Income? You should ask whoever is asking for it what they mean. But they probably mean Adjusted Gross Income (AGI).

It's on the Nebraska tax form thru TurboTax.

No.  Gross Income is before certain adjustments; such as an IRA deduction, Student Loan Interest deduction, and many others.

To further complicate things, there is also something called Modified Adjusted Gross Income, which has different definitions for different purposes.