There is nowhere to enter anything about the 3rd stimulus check on a 2020 tax return. The IRS is issuing those payments on its own timetable.
TurboTax cannot track your 3rd stimulus or tell you when it will arrive. The IRS is issuing 3rd stimulus checks on its own timetable.
You can use the IRS Get My Payment site to see what is expected for your 3rd stimulus check:
https://www.irs.gov/coronavirus/get-my-payment
https://www.irs.gov/coronavirus/get-my-payment-frequently-asked-questions