When did the rollover occur? If in 2019 the 401(k) administrator was required to issue a 1099-R no later then Jan 1, 2020. Contact the plan administrator for a copy.
If this was a regular 401(k) containing before tax money and not a designated Roth, then the conversion to a Roth will be taxable income.
A 5498 is information only and does not get reported anywhere.
A 401(k) rollover does not require a 8606.