I fyou want to fiddle only with the filename, then you could edit the text file to become a batch job and rename the files without the need to use MP3tag.
With MP3tag, you could import the data into the TITLE field and then compose a new filename with the tag field data.
If would now be much simpler to explain how to import the data into TITLE if you showed us the first (or some more) line(s) from the text file.
These are some lines I have with the filenames and the corresponding titles:
001.mp3 --> "001 - De Opener"
002.mp3 --> "002 - De Koe"
003.mp3 --> "003 - De Familie van Imraan"
004.mp3 --> "004 - De Vrouwen"
005.mp3 --> "005 - De Tafel"
006.mp3 --> "006 - Het Vee"
007.mp3 --> "007 - De Hoge Muren"
it looks as though the number of records and the number of files correspond.
Now try Convert>Text file-Tag
Enter the name of the source file.
Enter as import mask: %track% - %title%
Click OK.
Once the converter has completed the task, the fields TRACK and TITLE should be filled - check the files list for that.
Now use Convert>Tag-Filename to rename the files.
Format string: %track% - %title%
If you are not sure that you do it right, try it with a (a set of) sample file(s) first.