I don't understand your question. Your parents' taxable income is on Form 1040 line 15 of your parents' 2020 tax return. You find it on their 2020 tax return, or ask them to look at their tax return and tell you the amount. (The screen in TurboTax incorrectly says it's on line 11b, but you seem to already know that line 15 is the correct line number.) I assume you are looking for this because you are subject to kiddie tax. You will need some other information from your parents' 2020 tax return as well.
