Below are instructions to change workout tracking from Miles to Kilometers:

For Couch to 5k app:
  1. Open app
  2. Go to Settings tab
  3. Under APP OPTIONS, select Units with kg,km
For 5k to 10k app:
  1. Open app
  2. Go to Settings tab
  3. Tap Workout Options
  4. Under OTHER partenable Use Meters
Note: we cannot change workout tracking from Miles to Kilometers on 13.one app.