In Jain understanding, Jain Dharma is anādi-ananta — without beginning and without end. So it is not treated as a religion that “started” at a single historical point.

What is commonly discussed is the current time cycle and the appearance of the 24 Tirthankars in this era. In that sense, Bhagwan Mahavir lived around the 6th century BCE, which is much more recent than 3500 years ago.

So from the Jain view:

• Jain Dharma is eternal
• Tirthankars appear in different time cycles
• It is not correct, in Jain philosophy, to reduce Jainism to only “3500 years old”

If you want, I can also explain the Jain view of time cycles (utsarpini and avasarpiṇi) in simple words.