In Jainism, the "14 Purvas" are a collection of ancient canonical scriptures that were said to contain the most profound and complete knowledge of Jain doctrine, philosophy, cosmology, and conduct. The Purvas were originally part of the Drstivada, the twelfth Anga, which is now considered lost. Traditionally, only a few rare souls—such as Gandharas, Shrutkevalis, and omniscient (Kevalis)—were believed to have complete knowledge of the Purvas.

There is no standard "mantra" for all 14 Purvas in Jainism. However, Jain tradition sometimes reveres the knowledge of the Purvas and expresses devotion or respect through prayers or verses (stutis) dedicated to the scriptures and knowledge-bearers. But these are not specific "mantras" for each Purva.

If you are seeking the names of the 14 Purvas, they are as follows (in Prakrit):

1. Utpād
2. Agrāyani
3. Vīryānuprāvyā
4. Astināsti-pravāda
5. Jñāna-pravāda
6. Satya-pravāda
7. Atma-pravāda
8. Karma-pravāda
9. Pratyākhyāna
10. Vidyānuprāvyā
11. Kalyāna
12. Prāna
13. Kriyā-viśāla
14. Lokbindusāra

If you wish for a general prayer or mantra for knowledge, Jains often recite the Namokar Mantra (Navkar Mantra) with the intention of paying respect to those who have attained knowledge and spiritual purity, including the Kevalis and Shrutkevalis who knew the Purvas.

Namokar Mantra: ``` णमो अरिहंताणं। णमो सिद्धाणं। णमो आयरियाणं। णमो उवज्झायाणं। णमो लोए सव्वसाहूणं॥ ``` This mantra venerates the Arihants, Siddhas, Acharyas, Upadhyayas, and all Sadhus—the lineage of teachers and knowledge holders, including those connected to the Purvas.

If you meant a different specific mantra for the 14 Purvas or have another related inquiry, please clarify!