both the IRS and Turbotax only keep returns for 6 - 7 years.  so if used online for 2008 - 2010, they no longer exist. however, if all you need are the w-2s for those years, you can get copies from the Social Security Adm. there is a fee.

https://faq.ssa.gov/en-us/Topic/article/KA-02501 

You don't need your tax returns. Your tax return does not show who your employer was. That's why the lender is asking for the W-2s. Only the W-2 shows the name of the employer. And the W-2s themselves are not included in the tax return.

If you did not save your W-2s, the only way to get copies of W-2s that old is from the Social Security Administration, as indicated by Mike9241.