I cannot find last years tax returns on turbo tax and I do not have a Pin how do I calculate last years AGI (Adjusted gross income)?

[mesquitebean]

You don't calculate a 2017 AGI.  It was calculated on your prior return. You have to view it either on your 2017 return, IRS tax return transcript, etc.

Assuming you used Online TurboTax for 2017, I'll tell you below how to look for multiple accounts and regain access.

Try to find the online return first using the steps in my Answer below.   If push comes to shove, you may be able to immediately download a 2017 return transcript at the IRS website at the link below.  If you don't qualify to open a free IRS account there, you can order one to come by postal mail, but that normally takes 5-10 calendar days.   
<a rel="nofollow" target="_blank" href="http://www.irs.gov/Individuals/Get-Transcript">http://www.irs.gov/Individuals/Get-Transcript</a>

[mesquitebean]

If you prepared the 2017 return online but don't find it when you go to the Tax Home and look in "Your Tax Returns & Documents", then you likely have multiple accounts.

You can have up to 5 accounts that use the same email address for notification purposes.  A User ID may be an email address, but it doesn't have to be.  It might be only part of an email address, or it can be anything at all.

To get a list of your User IDs and recover account access, you can use the tool at the link below.  Try using your phone number first.   After that, if necessary, then run the tool on your email address(es) you can access.

NOTE: Before running the account recovery tool below, log out of all Intuit accounts including this user forum, or you might end up in a loop.  Then clear your browser Internet cache, close your browser, then reopen it, and go to the link below.  You may wish to copy this link so you can paste it into the new browser session.

https://myturbotax.intuit.com/account-recovery

If still no luck after running that on your phone number and email address(es) that you can access,  here's another method.
Go back to the tool again, but this time leave the data field blank, and choose the small blue link that says "Try something else", and it will look you up by SSN and other parameters.