If you are trying to do your 2019 tax return, you should contact your employer to obtain your W-2 from that year. If they are unable to provide it, you can also create an account with the IRS from their main page. Once you are logged in, click on Get Transcript. You can leave the Customer File Number blank. Then look for 2019 under Wage & Income Transcript.
If you are trying to file your 2021 tax return, you do not need your 2019 W-2 at all. You can elect to use your 2019 earned income if it is higher than your 2021 earned income and yields a larger earned income credit. You do not have to use the 2019 earned income. If you did file in 2019, you can get your earned income from your Form 1040 Line 1 if you got a W-2 in 2019. If you were self-employed, your earned income in 2019 would be Form 1040 Schedule 1 Line 3 - Line 14 + Form 1040 line 1.
If you do not have this number, or your earned income in 2019 was lower than 2021, you can just click No on the Let's make sure you're getting your max credit screen.
