Need to know CISAM definition to create schema

Hi all, I have an old application written using CISAM.Our goal is to convert all data into Oracle tables. Unix admin is going to extract data into ASCII files. I'm planning to use SQL*Loader. When I log into unix, all I see is a bunch of idx files, .dat files, udat files and .h files. Being new to all this, I have no idea how can I get CISAM file definitions to create schema or Oracle tables? Other than looking into each data file manually. Also we don't have Informix SE, which I think would have helped. Any help will be appreciated? Thanks.