That doesn’t work that way. You can use WPML for translation but it will translate the word “miles” to whatever the word for Miles is in the translation, it wont convert distance from and to metric, that is a mathematical formula, not text.  We used to have something called MultiMap but the logistics got so tangled that it needed a lot more work and very few people bought it.

It works the same way Google Maps does, it will not show you how many km away unless you toggle the google map from km to miles.  i,e, try it, search from Commercial Google MAPS , for instance I searched for Rome, it came back with miles. If I click on the bottom right hand corner it will convert, toggle to miles or KM.