You need the 2017 AGI to e-file the 2018 tax return.
To access your prior year online tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/
Scroll down and on the section Your tax returns & documents click on Show. Click on the Year and Click on View adjusted gross income (AGI)
You can also get free transcripts of your federal return from the IRS - http://www.irs.gov/Individuals/Get-Transcript
