Return not received

The IRS does not confirm receipt of mailed returns.  Per the IRS:

COVID-19 Mail Processing Delays

It’s taking us longer to process mailed documents including:

• Paper tax returns, and
• All tax return related correspondence.

We are processing all mail in the order we received it.

Do not file a second tax return or call the IRS.

Refunds | Internal Revenue Service (irs.gov)

You don't get confirmation for mailed returns.  Only from the post office if you got a tracking number when you mailed it.