You are able to do this Shabar mantra chanting for eleven, 21, 31, or 41 times, the place and time of mantra chanting need to be a similar for the number of times you wish to do sadhana. You should use Rudraksha or Tulsi rosary to chant the mantra. https://arthuraungy.answerblogs.com/32553771/not-known-facts-about-most-powerful-sarv-karya-sidh-shabar-mantra-karya-siddhi-shabar-mantra-most-powerful-shabar-mantra