B: We need is a source for exchange rates. There are some published connectors, but you also use a free service called Exchange Rates API, which are based on the European Central Bank, and create a custom connection.
Now that we have our custom connector defined and have a way to request the latest exchange rates, the next step is to create a Power Automate flow that will update all of currencies setup in our Dataverse environment.
Dataverse is a multicurrency system, in which each record can be associated with its own currency. This currency is called the transaction currency. The multicurrency features enable users to perform financial transactions like opportunities, quotes, orders, and invoices in multiple currencies. This feature also provides a currency choice to the end user when a financial transaction occurs.
Reference:
https://readyxrm.blog/2021/03/10/updating-currency-exchange-rates-in-dataverse/