Enter the value of your Roth IRAs on December 31, 2020 How do I know the value of my IRA?

You should have a year end statement from the IRA Account.  Maybe wait for it.  Are you sure they want the 2020 year end value?  Maybe it wants the 2019 December value.

Nowhere does 2020 TurboTax ask for your 2019 year-end value in IRAs.  TurboTax asks for your 2020 year end value in Roth IRAs if your entries indicate to TurboTax that you have an excess contribution in your Roth IRAs because the excess-contribution penalty is calculated on the lesser of the amount of the excess or the year end balance.

Since Forms 5498 from your Roth IRAs might not be available to you until May, you'll need to obtain the December 31, 2020 balances from your year-end Roth IRA account statements.