How can I get my last year AGI if I can't get into my old account

The easiest and quickest way is to use the IRS webpage I'm linking below.  You'll be able to access your 2019 transcript (an abbreviated return) which will include your 2019 AGI.

 

Get Transcript | Internal Revenue Service (irs.gov)

Is there a way to get into my last year (2019) TurboTax account?  I've misplaced the paperwork with all of my log in information on it 

Yes, TurboTax can help you recover your account.  See the TurboTax FAQ I'm linking below for information.

 

Account Recovery Request for your TurboTax Account (intuit.com)

 

ADDED AFTER ORIGINAL ANSWER:

Try this first:

Forgot your TurboTax Online user ID or password?