Are you asking how much your refund was for the 2019 return you filed in 2020? Or are you asking for the 2019 AGI so that you can e-file your 2020 return?
You can look at your 2019 return:
Where do I find my AGI?
Your 2019 tax return shows your 2019 Adjusted Gross Income (AGI) If you filed a joint return then the AGI is the same for each of you.
Form 1040 line 8b
If you are using the same TT account that you used last year, you should also be able to find this number in your Tax Home for 2019
If entering the amount from your 2019 tax return does not work, then try entering “0” instead. If that does not work and you still cannot e-file, then print, sign, and mail your tax return.
You can get a free transcript of your past return from the IRS:
Note: If you filed late or amended your return, your correct 2019 AGI may not be in the system.
You have to access your own account and/or print it for yourself using exactly the same account and user ID that you used when you prepared the return.
Many people have multiple TT accounts and forget how to access them. Log out of the account you are in now.
Or did you use the desktop version of TurboTax? If so, the files are on your own hard drive or any backup device you used like a flash drive.
To get a copy of your previously filed returns prepared with online TurboTax https://ttlc.intuit.com/questions/1900748-how-do-i-get-a-copy-of-a-return-i-filed-in-turbotax-online