Are you looking for last year's AGI number, so you can e-file? Every year when you e-file, you have to choose a 5 digit self-select pin.
When you e-file this year's tax return, you have to enter either last year's AGI number OR last year's 5 digit self-select pin, not both. Only enter one of those fields when you are trying to e-file, not both.
How do I find last year's AGI? If you can't remember your 5 digit pin, try using zero for the AGI number. If it rejects, review the linked help article. On your 2023 tax return, your AGI was on Line 11.