Tracking cost basis - does 401k count as "Traditional IRA"?

I think this is a simple question, but the answer isn't obvious to me. On TurboTax, I'm trying to fill in the fields for tracking my cost basis for my Roth IRA. In 2017, I converted a 401k from my previous employer to a Roth IRA. I think it was a trustee-to-trustee transfer; I got a check for the 401k, then sent it to the company with whom I had a pre-existing Roth. They put the check in a "Rollover IRA brokerage account," which I then transferred to my pre-existing Roth.

 

So...to track my cost basis, TurboTax is asking me to enter all previous contributions, but NOT to include amounts converted from a "traditional IRA." I am aware that a 401k is not technically considered an IRA, but for this purpose, would it be considered a traditional IRA? That is, would I NOT include the amount converted from my 401k in the contributions section, then fill in the amount later when the program asks about conversions from traditional IRAs?

 

Thank you!