How do I find my state gross income?

Look at the W-2's and Form 1099's you received that show state income.

Are you looking for gross income on a state tax return that you previously filed? If so, which state is it, and what year? Every state has different forms.

Why do you need to know your state gross income? State gross income might be defined differently for different purposes. But again, every state has different rules, so which state is it?

Yes

@hasah22 What are you trying to do?  You inexplicably replied "Yes" to a thread that has had no activity for nearly a year.