TTax does not keep tax returns for that long. It is up to you to keep copies of your tax returns each year.
You should:
print and keep a paper copy of your return;
you should also save a .pdf copy of your return;
and you should also keep/save the .taxnn file for each year. (where nn is the specific tax year of the return
As a last resort you can contact the IRS and request either a Transcript or a Copy for the desired years.
There is a charge for copies; however, a transcript of the return is free.
https://www.irs.gov/newsroom/how-to-get-tax-transcripts-and-copies-of-tax-returns-from-the-irs
