How do I report US Treasury Note face value on Schedule 3 when the face value for the Notes are in USD. What exchange rate do you use for the purchase of the notes?

How do you report USD Treasury Note interest on Schedule 3. The form asks for the face value.  What exchange rate do you use?  What exchange rate do you use when the Notes were purchased in the past at some exchange rate and later redeemed at the exchange rate at the time of redemption. Still no answer on how to report more than two entries on Schedule 3.  I am not sure TurboTax can work for this type of investment tool.