Backdoor Roth: having both 2019 and 2020 Traditional IRA contributions in 2020

I created my first Traditional IRA account and also my first Roth IRA account in 2020.

 

I contributed $12,000 ($6,000 for 2019, and $6000 for 2020) to the Traditional IRA account. I then converted all the $12,000 amount in the Traditional IRA account to my Roth IRA account (i.e., backdoor Roth method). All of these were done before 4/15/2020.

 

Do I need to amend my 2019 tax return to indicate that the 2019's $6,000 Traditional IRA contribution happened sometime between 1/1/2020 to 4/15/2020?

Update: From my research online, this should not be necessary because the 2019's contribution mentioned is non-deductible. However, I need to file Form 8606 for both 2019 and 2020. In this case, how should I file Form 8606 for 2019? Thanks!