Roth conversion

I am disabled age 50. Most of my income is SSDI. Want to use TTax 2023 to estimate taxes due for a 2024 conversion of part or all of my standard IRA to a Roth. Confused by what to enter on a mock 1099R: Distribution code? Section B questions?

Of course (as many newspaper articles are suggesting these days), my goal is to pay the taxes now when my income is low and not a few years later when tax rates will likely be higher.