How do I enter a backdoor Roth IRA conversion, when I am rolling over multiple year's worth of traditional IRA contributions?

OK, so here's what I did.

  1. Over the past few years I contributed to a traditional IRA.  Those contributions totaled $9,250.  I did not take tax deductions on that money (I made over the limit).  I have form 8606s for those years. 
  2. In 2021 I made a $6,000 deposit towards my 2020 limit at the start of the year, and 6,000 later on for my 2021 contribution. Again, I was over the income limit.  I don't have a form 8606 for this because I am doing the taxes now.  
  3. In 2021 I converted to a Roth IRA, and the total amount converted was $28,531, my contributions totaled $21,250
  4. How do I enter all of this into Turbo Tax? The link here from the Turbo Tax folks seems to only apply if you only have one year's worth of money rolling over.  Am I supposed to just say that the full $21,250 was contributed this year? 

When I look up tutorials it says to enter the contributions under the Deductions & Credits section, but that appears to be ONLY for 2021, these contributions go back years. Can someone who has done this before in Turbo Tax please help?