While you cannot usually pick an individual piece by its exact index number, you can influence the order: What You Need to Know Before Downloading a Torrent
If you are looking to manage how pieces or files within mmmmmm.torrent are downloaded, here are the most effective methods: Select Specific Files Download File mmmmmm.torrent
Instead of downloading the entire torrent, you can choose only the specific files you need: While you cannot usually pick an individual piece