If you used TurboTax last year, you can access your return by logging in using the same TurboTax account that you used to file your 2018 return. Please follow the steps provided below.
1. Go to Tax Home in the left menu.
2. Under Your tax returns & documents, go to Download/print return (PDF) (select Show if not visible).
https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/00/27010
You can also get your AGI by ordering a free transcript of your 2018 return or purchasing a full copy from the IRS. Please see below for more information.
https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/00/25947