Only the 3rd stimulus payment is reported on the 2021 tax return.
If you did not receive the two economic stimulus payments, EIP1 and EIP2, in 2020 or in January 2021 you should have indicated that on your 2020 federal tax return so you would have received them on the 2020 tax return as a Recovery Rebate Credit on Line 30 of the Form 1040.
If you did not receive the Recovery Rebate Credit on the 2020 tax return you will have to amend the 2020 return to enter the credit.
See this TurboTax support FAQ for amending the 2020 tax return - https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-return/00/27439