It looks like you’re asking about Bharata Kshetra and Mahāvideha Kshetra in Jain cosmology (Jambūdvīpa).

• They are contiguous regions within Jambūdvīpa, not separate islands.
• Bharata Kshetra lies at the southern side of Jambūdvīpa.
• Mahāvideha Kshetra is the broad central belt around Mount Meru.
• The practical “boundary” between Bharata and Mahāvideha is the Himavān (Himavan) mountain range. So there isn’t a gap to measure; they meet at that range.

Different texts describe the widths of mountains and rivers in yojanas, but they do not give a separate “distance between” these two kshetras—because they touch at the Himavān range. Digambar and Shvetambar traditions both present them as adjacent regions divided by this mountain belt.