How to save iteratively each object in list with the corresponding index, that it has been marked by

I have a list of dataset

list_dataset = [data1, data0]

for every object in it, I would like to save each dataset with the corresponding index (0 and 1), that the dataset has been marked by. I do not know how to proceed about this:

for I in list_dataset:
    i.to_json(r'C:\Users\PC\Data_indexed(??).txt')
    i.to_csv('Data_indexed(??).txt', sep='\t')

Could you possibly might suggest something? Thanks