TurboTax does this calculation behind the scenes and does not provide a way to view the calculation. For most people MAGI for the purpose of a Roth contribution is AGI minus the amount of any conversions to a Roth IRA. In less common cases there are a few additions to AGI. The entire calculation, which TurboTax implements correctly, is described here:
https://www.irs.gov/publications/p590a#en_US_2025_publink1000230985
For TurboTax to treat the code-7 distribution as a Roth conversion, you must indicate that you moved the money to another retirement account and that you converted the entire amount to Roth.
