I assume you are asking about a 2018 W-2 rather than a W-4. TurboTax does not have W-2s, but you can open your 2018 tax form and look at the information you entered from you W-2 when you filed it. Here is how to access prior year returns filed using the online product: https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/00/270...
If you filed using the CD/download product, the only copy of your tax return is on your computer. If you saved a copy of your tax return with all the documents, you should be able to find the pdf of the return on your computer.
You can get a W-2 transcript from the IRS using this link: https://www.irs.gov/taxtopics/tc159
