They had found the WARC-format domain index at index.commoncrawl.org and wanted to know whether any index exists for the .WET plain-text format files too. If not, they asked how to convert a WARC object address (an s3://commoncrawl/crawl-data/... path) into the address of the corresponding WET file. This is a timeless path-mapping question, still valid despite the thread being from 2017.