See the instructions in the TurboTax FAQ below to get a copy of your extension.
"How do I print my 4868 extension form after e-filing it through TurboTax Easy Extension?"
https://ttlc.intuit.com/replies/4736887
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***