With Listify the location of your listings is based on the set radius. You can use the location slider to change the radius of your location to which your listings are based.
With the location slider, you can either use a radius based on the units of your base country.
Therefore, to change the radius units from kilometers(KM) to miles (mi) you would have to change your base country.
To do so proceed to WordPress > Appearance > Customize > Listings > Labels & Filters Base Country.
In the above example the base country is set to the United Kingdom [UK]. Therefore the radius units will reflect as Miles [Mi]
If we use a different base country that supports the kilometers units then the radius will display with these units.