Splitting Filename to Track and Artist?

I have tons of downloaded music, whose filenames are mostly just "artist - track name". I want to split the file name in the action window, but all I see is "FILETYPE" and "FILEOWNER". Which one from the "split by separator" would give me access to the filename of the song? Thanks in advance!
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You are using the wrong action because you don't want to split a tag-field. This is for making 2 same tag-fields out of 1.
What you need is the action-type "Guess Values" or you can use the converter "Filnename -Tag" which is easier to use because it gives you an immediate preview of your format string.

Converter Filename - Tag:
Format String: %artist% - %title%

Action Guess Values:
Source Format: %_filename%
Guessing Pattern: %artist% - %title%