if it’s a one-time action, @Terry-R’s suggestion is spot on, and you don’t need to read my post.
However, if it’s an action you are going to take a lot, I would suggest recording a macro:
Macro > Start Recording Search > Mark FIND WHAT: \d{3}$ (this assumes it’s always a digit, like in your example; if it is just the last three characters, whether it’s digit or not, then .{3}$ instead Uncheckmark Bookmark line Checkmark Purge for each search Mark All Copy Marked Text Clear all marks Close File > New Edit > Paste Macro > Stop Recording Macro > Save Current Recorded Macro Give it a name that makes sense to you (CopyLastDigitsToNewFile or something) Give it a keyboard shortcut if desired.From now on, you can run the macro to copy those last digits/characters to a new file.