In Jain Padmapurana (the Jain Ramayana by Acharya Ravishena), the story is mainly about:

• Padma (Rama)
• Lakshmana
• Sita
• Ravana and related Ramayana characters

The Mahabharata hero Karna does not have an important role there. Padmapurana is a Ramayana‑based Jain Purana, not the Jain Mahabharata.

If you are asking about Karna of Mahabharata in Jain tradition, then you have to look into the Jain Mahabharata texts (like Harivamsa‑Purana etc.), not Padmapurana. Those texts present the Mahabharata story in line with Jain principles (ahimsa, karma, non‑divine heroes, etc.).

You can read more about Jain Padmapurana and Jain Mahabharata here