If you did the original contribution in 2020 then you should have reported it on the 2020 return and it would be on the form 8606. If you then made the conversion in 2021 when you enter the 1099-R read the screens carefully to indicate you had prior year basis from form 8606. Step 1 is only done in the years contributions are made ... step 2 is for the years conversions are done. You could use one or both steps in a single tax year.
If you failed to file an 8606 on the 2020 return an amendment is needed.
