You can change the unit that you post your own distances from.
Login and go to "My Settings" from the main menu
Login an go to the main menu.
Go to "My Settings"
You can log your distances in whatever unit you prefer but it will be displayed based on the preferences that the group mission admin has set up. e.g If they have set the mission to "miles" then all distances will be shown in miles (a conversion takes place if you posted in km)
You can post in any unit but they will be displayed in miles as this is the base unit for all Conqueror challenges.