You can do this Shabar mantra chanting for eleven, 21, 31, or 41 days, the place and time of mantra chanting should be exactly the same for the amount of days you need to do sadhana. You need to use Rudraksha or Tulsi rosary to chant the mantra. It https://glowingdirectory.com/listings13056798/indicators-on-most-powerful-sarv-karya-sidh-shabar-mantra-karya-siddhi-shabar-mantra-most-powerful-shabar-mantra-you-should-know