2020 is a closed year. There is no point in filing a tax return for 2020 to correct this error.
You should correct your records to reflect the difference between the reported contribution and actual contribution and maintain them but there is no point in reporting this. The amount was moved to the Roth in 2021 according to what you put up there and so it was a backdoor Roth contribution and not a deductible IRA contribution. So there is not an overcontributed amount that has been sitting in your traditional IRA for years.
The only issue is the deduction for 2020 that you received and should not have. Since that is the case this issue is closed already.
If you decide that you have to amend the return because you won't feel right otherwise you will need to download forms from the IRS website to do the amendment and copy all of the numbers from your copy of your 2020 return. (You may also be able to find copies of 2020 TurboTax software on eBay.) There is no online support for an amendment from that far back.
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