I did not use turbo tax until this year. how do i get my 2019 agi?

Did you prepare and file a 2019 return somewhere else?  If so, that would be a good starting place--with whomever prepared it.

If you didn't file a 2019 return at all, you would use an AGI of 0 (zero).   Also, if you filed a 2019 real late, such as mid-November 2020 or later, you would use an AGI of 0.   If the IRS was very late in processing your 2019 return (i.e., they didn't finish it until after November 2020), you can try an AGI of 0.

If you qualify to open an IRS account, you can download a free 2019 tax return transcript.

https://www.irs.gov/individuals/get-transcript

Also see this FAQ:

FAQ:  How do I find last year's AGI?

https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/01/25947