How can Fijian-Indians trace back their ancestry to India?
There is an Indian Diaspora scattered in many countries with a situation like what you describe in Fiji. Indians were forced out or lured to distant shores like Fiji, Malaysia or South Africa where they found that they are nothing more than indentured labor and could not even return if they wanted to. After many generations, they have lost touch with their roots and since no genealogical records were maintained, do not even know where in India they originally came from. It is often possible to guess from their names which region of India they came from. The language(s) they spoke at home can also give a clue. The best you can do is to trace the family history to the point they arrived in Fiji and hope that you will be able to make a connection to India. Good luck!