Here are some options:
Please see What if it's February but I still don't have my W-2?
Use the TurboTax Easy Extension. It's the fast, easy, and secure way to e-file your federal tax extension.
Note: Filing an extension doesn't give you additional time to pay owed taxes, which are due May 17, 2021 (it's the same date for taxpayers out of the country). If you can't pay owed tax by the deadline, always file an extension so you can avoid the late-filing penalty, which is up to 10 times higher than the late-payment penalty.
It will be incorrect when you file it and then you will have to amend when you dig up the missing W-2. Or you can ask for an extension and file later when you get it. But an extension does not give you extra time to pay tax you owe. If you expect to owe tax you need to pay your estimated tax due with your extension request.
If you are getting a refund there is no penalty for missing the deadline.
https://ttlc.intuit.com/community/tax-topics/help/how-do-i-file-a-tax-extension/00/1005116
W-2's come from your employer, and they have until February 1 to issue it. Some employers allow you to import the W-2 through the software, but for security reasons you still need information from the actual W-2 to import it. You might need to phone, drop in, email and/or snail mail an old employer to make sure they know where to send your W-2.
https://ttlc.intuit.com/questions/2561916-how-can-i-get-a-copy-of-my-w-2