Add part of the filename to the title tag

Can someone help me please?
I have a bunch of Whitburn pop files in the format:
Year_number - artist - title
1951_001 - Johnny Ray & Four Lads - Cry 80 M (3.02).mp3
The current title tag is Cry.
I would like to change that to 1951_001 Cry
I tried Convert but it adds the info after Cry in the filename.
I also tried some actions, but couldn't figure out how to extraxt the year number part of the filename.

Try an action of the type "Guess value"
Source: $regexp(%_filename%,(.*?) -.*,$1) %title%
Target: %title%

If I create an action of type "Guess Value", I get prompted for source format and Guessing pattern. It does not prompt me for target. Thanks for the response, but I need more help. If I use an action of type "Replace Value" I think it would do what I want, but I can't figure out the correct syntax for the field, "Replace with".

ok, there are 2 strings that you have to enter. One is the "Source format"(?) and the other one a format string as target. I have the German version so apparently the translation does not quite match.
An action of the type "Replace" will not really work.

I figured out a 2-step conversion that works.

1, Convert filename to tag with format string %year% - %dummy%
That puts the Year_number from the filename into the year field. It overwrites whatever was in the year field, but I can live with that.

  1. convert tag - tag with TITLE in the field and %year% %title% in the format string.
    Thanks for looking at my problem and making suggestions.

If you use a user-defined field like %myyear% instead of %year% in

the you do not loose the original content of YEAR.

The second step would have instead of

%myyear% %title%

Afterwards you may delete MYYEAR.
But all this could be accomplished in just one step with the "Guess value" example.

It's called "Guessing Pattern".

I am happy with my solution. It works on all my many files. Thanks for all the responses, guys.