If you e-filed your 2020 tax return there will be an Electronic Postmark Report which will have the date/time the tax return was transmitted and the date it was Accepted by the IRS, if Accepted. The Postmark Report will be included in the PDF of the 2020 tax return.
If you mailed the tax return TurboTax has no information on a mailed return.
To access your 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 section Your tax returns & documents. Click on the Year and Click on Download/print return (PDF)
If you used the desktop CD/Download editions installed on your computer, the only copy of your tax data file and any PDF's will be on the computer where the return was created. TurboTax does not store online any returns completed using the desktop editions.