IRS sent letter requesting to resend copies of my e-filed 1040SR page 1 to 3 and label them DO NOT PROCESS. How do you do this?

To access your current or prior year online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/

Scroll down to the bottom of the screen and on the section Your tax returns & documents.  Click on the Year and Click on Download/print return (PDF)