Steps per se cannot be converted into minutes or points and vice versa (points into minutes).
However, if the intensity of your walk or run was moderate or high, you will earn training points which will count towards the goal in specific challenges, e.g. a Movement Challenge.
You can participate in as many of your company's challenges as you like or create them yourself. If you participate in two step challenges, your steps count for each of these challenges. If you also take part in a mindfulness points challenge, you can only progress with mindfulness points (not steps).