They never send you anything to show they received it when you mail a return. If you want to know it was received you need to use a mailing service that tracks it like certified mail or UPS.
MAILED RETURNS
Per the IRS website IRS Operations During COVID-19: Mission-critical functions continue: The IRS is not currently able to process individual paper tax returns. If you already have filed via paper but it has not yet been processed, do not file a second tax return or write to the IRS to inquire about the status of your return or your economic impact payment. Paper returns will be processed once processing centers are able to reopen.
If you mail a tax return (or a payment) to the IRS, it is a good idea to use a mailing service that will track it like UPS or certified mail so you will know it was received.
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.
TurboTax will not know anything about your mailed return, and will continue to show “Ready to Mail” on your account. TurboTax will not know that you put your tax return in an envelope and took it to a mailbox. TurboTax does not get updates on mailed (or e-filed) returns.
When the IRS finally opens its mail and begins to process mailed returns you can check the status on the IRS site. https://www.irs.gov/refunds
State returns have to be mailed to the state.
https://ttlc.intuit.com/questions/1899433-how-do-i-track-my-state-refund
https://www.cnn.com/2020/04/20/politics/irs-mail-trailers-covid/index.html
How do I find & print my federal & tax return in turbo tax?
Are you using the Online version? Did you first try Efiling?
How to mail a return from the Online version
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS received the return. Don’t forget state.
Important! Mail Federal and State in separate envelopes and mail each year in separate envelopes.
Where to mail federal paper returns
https://www.irs.gov/uac/where-to-file-paper-tax-returns-with-or-without-a-payment
How do access & print my completed turbo tax Federal & state documents already finished ready to print & Mail?
Click on Add a State to let you back into your return.
Can you find your return? That's common to end up with multiple accounts. First LOG OUT of whatever TurboTax account you're logged into right now. Then use this TurboTax account recovery website to get a list of user ID's for an email address. Run the tool against any email addresses you may have used
https://myturbotax.intuit.com/account-recovery/
If you used the Desktop CD/Download program then the only copy is on your computer and not saved or stored online.