Rename file except last 3 digits of name

All files have been numbered (ex. 001-999), prefixed names vary in length, names include spaces, dashes, hyphens, etc. (ex. Another-Western - John-Wayne-030.mkv, An-Old-Black-&-White - Tom-Selleck-002.avi). Desire to save file numbers (which are not complete numerical order [missing some numbers at this point]. In other software might look like "length(filename)-3".