If you used the CD version to prepare a tax return, the only place it exists is on the physical computer the software was installed on, and used to prepare and file that tax return.
If you used the online version, then prior year tax returns are available in the user account that was used to prepare and file those tax returns. Turbotax does not have access to user accounts. Only the user that prepared/filed the tax return does.
While a copy of the return does cost money from the IRS, you can get a transcript for each year for free. You can get it online, and only takes a few minutes at https://www.irs.gov/individuals/get-transcript. Most likely, all that's needed for the legal front is transcripts, and I'd expect that would be fine.
You can also provide them a signed 4506-T which you can get at https://www.irs.gov/pub/irs-pdf/f4506t.pdf and they can submit the request themselves.
