It is way too late to get a refund for a 2011 tax return, but if you want to file the return you can get the form from the IRS:
https://www.irs.gov/forms-pubs/prior-year
Our prior year products go back to 2014. We would not be able to support a 2011 return.
https://turbotax.intuit.com/personal-taxes/past-years-products/