Several questions:
Do you fill the tags or do you only rely on the filename to have the information about the track? If the tags are empty then MP3tag will sort the filename.
If you have filled the tag "track no" (or as internal variable: %track%) the you may click on the column header in the MP3tag's list view to sort by that column.
If you have not yet filled the tags then use the converter "filename tag" to retrieve the information from the filename (before you delete it). Once you have imported the information, it is much easier to manipulate it and to rename the files the way you like it.