Currency change

The currency is dependent on the country your Apple ID is set to.

You would need to change the country to a different one with the currency you want to use: link-> Change your Apple ID country or region - Apple Support

Open a currecny converter website using Safari, i.e. this one:--> https://www.xe.com/currencyconverter/convert/?Amount=1&From=USD&To=LKR

Regards

Giulio