If you used tax preparation software to complete the tax return you should be able to get a copy of the return. Or if you used a paid tax preparer they can give you a copy.
Go to this IRS website for free federal tax return transcripts - https://www.irs.gov/individuals/get-transcript
For a fee of $43 you can get a complete federal tax return from the IRS by completing Form 4506 - http://www.irs.gov/pub/irs-pdf/f4506.pdf
What exactly do you mean by "upload" a previous tax return? What are you trying to do? Are you trying to put 2019 data into TurboTax to start a 2020 return? Or do you mean you just need a copy of a previous tax return that you prepared somewhere else?