It depends on when and how you prepared the 2017 amended return.
If you prepared the 2017 amended return prior to November 2018 when 2017 online TurboTax was still operational, then the 1040X should be in the 2017 PDF available in your online account in the section "Your Tax Returns & Documents." If you try to download the PDF, and access to the return is locked, we can tell you how to pay to unlock it. Typically that involves upgrading a 2018 Free Edition return to PLUS and paying 19.99 by credit/debit card. We can tell you all the steps.
If you amended the 2017 return AFTER online TurboTax shut down for that tax year, then you would have had to do so in downloaded "amend software" on your computer. In that case, any 2017 tax files containing the Form 1040X would be stored on your computer.
