האם ניתן לתבוע הלוואה שניתנה לפני 30 שנה עם ריבית והצמדה?

Shalom, my father in law passed away three months ag o, I lended him money to buy 7% of his house some 30 years ago. He wrote he owes me a fixed sum ($10,000) but not the interest on that money.My sisters say that this is an old loan and the law of Hityashnoot prevents me from charging interest. I lived out of Israel for 15 years, is there anyway I can get the money in it's real value ? In Hebrew please...