Clarification please. After converting from a 401(k) to a traditional IRA, you write:

The next step involves taxes. If you then want to convert the
new traditional IRA to a Roth, and your trustee accepts the Roth,
you can direct the trustee to make that conversion. Tax will be
due on the non-taxed amount of the conversion....

Do I interpret this correctly: In this process, you're saying that I was able to roll over both taxed and non-taxed funds from the 401(k) to a traditional IRA? I thought that I had to exclude the already taxed funds from the rollover.