If you used Turbo Tax to file 2018 returns & then again to file 2019 returns, it will just come up automatically.  Otherwise, you can just create or ask for a new e-filing pin #.

You no longer need a PIN number from last year to electronically file your return as the IRS did away with this method of security validation.  Instead you will be required to use your 2018 AGI (Adjusted Gross Income) in order to electronically file your federal tax return.

If you used TurboTax last year you can view your 2018 AGI by selecting Documents on the left hand side of your screen.  Select View Documents from: Select 2018 on the drop down menu.

OR

You can obtain a copy of last year's tax transcript online using IRS link:   Transcript 

OR

If you have a copy of your 2018 tax return, your AGI is located on line 7.