I contributed $6000 to traditional IRA in 12/2020 and converted to ROTH in 01/2021. Do I report this $6000 in 2020 or 2021 tax return?

I contributed $6000 to traditional IRA in 12/2020 and converted to ROTH in 01/2021. Do I report this $6000 in 2020 or 2021 tax return? based on https://ttlc.intuit.com/community/entering-importing/help/how-do-i-enter-a-backdoor-roth-ira-convers..., there are two steps for endtering backdoor ROTH IRA. Do I have to do step 1 in 2020 tax return and step 2 in 2021 or can I do both steps in 2021 tax return?