To complete and file prior year tax returns, 2018 thru 2016, using TurboTax you would need to purchase, download and install on a personal computer one of the desktop editions for each tax year required from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
A prior year tax return can only be printed and mailed, it cannot be e-filed.
I've not filed taxes in several years, how many years back taxes can file on turbo tax?
You need to purchase each year separately. The 2016 tax year is the oldest past year return supported.
You must use the CD/download product to prepare and file prior year tax returns. The software is available for 2016,2017, and 2018. Each year must be purchased separately. Prior year returns must be printed and mailed. They can't be efiled. See here: https://turbotax.intuit.com/personal-taxes/past-years-products/
For years prior to 2016, you would have to find a paid preparer with software that old or you could download the forms from the IRS web site and complete them by hand.
I highly recommend you seek local professional assistance to file that many years or if you feel you can fill out the forms yourself they can be gotten on the IRS website. Any refunds from 2016 and older are forfeited so start with the 2017 - 2019 returns and work back to the older years.