Answer

In Jain cosmology, there are generally 15 Karma-bhumi.

Explanation

They are counted as:

• 5 in Bharat Kshetra
• 5 in Airavat Kshetra
• 5 in Mahavideha Kshetra

So the main names are:

• Bharat
• Airavat
• Mahavideha

These are the three regions where the 15 Karma-bhumis are counted.

Spiritual Understanding

Karma-bhumi is the land where:

• human effort is possible,
• karma is accumulated and destroyed,
• and spiritual progress toward liberation can happen.

That is why Karma-bhumi is very important in Jain Dharma.

Takeaway

Total Karma-bhumi = 15 Main regions = Bharat, Airavat, Mahavideha

If you want, I can also list the 15 sub-regions name-wise in a simple table.