Answer

If you mean the commonly used Jain Shanti Dhara mantra, one widely given Japya Mantra is:

Om Hreem Vishva Shantikaraya Shri Shanti Nathaya Namah

It is often recited 9, 27, or 108 times during Shanti Dhara. ( encyclopediaofjainism.com)

Explanation

In Jain puja tradition, Shanti Dhara is generally performed after Abhishek of Lord Jinendra. One Jain source specifically gives the above mantra as the Shanti Mantra for this practice. ( encyclopediaofjainism.com)

Spiritual Understanding

This mantra is a prayer for peace, inner calm, and removal of disturbances. In the Jain tradition, it is connected with devotion to Shri Shantinath Bhagwan, the 16th Tirthankar, whose very name is associated with peace. ( encyclopediaofjainism.com)

Takeaway

If you want, I can also give you:

• the full Shanti Dhara text
• the Hindi meaning
• or the step-by-step way it is recited.