To order and receive parts in a foreign currency, you will first open up the purchase order application and create a new purchase order to the applicable vendor.
You can see if that vendor for your purchase order is set up for currency on the purchase order, as seen below in yellow. This is set up in the vendor record, where a currency type will be denoted. You will add the part at your regular cost, in your currency.
Then, when the parts are received in, you will see the currency conversion set up in the receiving record. Note that the cost of the part is 5.00, but on my receiving record it shows the cost of 3.79 due to the currency conversion.
That will convert back to 5 dollars in the parts record, leaving your payable 3.79 in the exchange currency but selling the part in your original currency.
In parts setup, the pre-currency cost for markup is a pricing determination, not for costing. The cost price on the parts record is typically determined from the last receiving date unless it is being updated from a price file instead. You can also update it manually if you so choose by updating the field in the parts record.
There is also an option to not update cost on the purchase order record should you choose not to update the cost on the parts record from a receiving.