You can read below about where to find your AGI.
https://ttlc.intuit.com/replies/3301618
How to get a copy of you return if you did use TurboTax Online:
https://ttlc.intuit.com/replies/3301525
If you didn't use TurboTax Online to file last year (and you don't have a copy of your return) then you'll need to request transcripts from the IRS or file by mail:
https://ttlc.intuit.com/replies/3301999
https://ttlc.intuit.com/replies/4170366
If you did, but can't access your TurboTax Online account or your prior year data isn't showing up in your account, then read below:
https://ttlc.intuit.com/replies/5667209