Currency Updater application will need to use 5 fields to show the proper converted amount.

1. Amount field (Currency or Number type): used to calculate the converted amount
2. CurrencyISOCode: used to look the proper Dated Conversion Rate
3. Date field (Date Type): used to look the proper Dated Conversion Rate
4. Dated Exchange Rate (Number Type): Where the app will populate with the conversion rate for the currency and date. Ensure to grant permissions all users creating or updating records.
5. Converted Amount (Formula field) like the image below