A tax refund is not what is needed to e-file a 2018 tax return.  You need the 2017 AGI from the filed 2017 federal tax return.

• Form 1040 – Line 37
• Form 1040A – Line 21
• Form 1040EZ – Line 4

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