Does the Edit > Find and Replace function do what you want?
Do not PM me asking for help with Aegisub, Automation, karaoke or anything like that, I won't reply.
Ask your questions in the public forums. Use the Search function, somebody probably asked the same question before.
All rights reserved to call you insults if you ask poorly thought out or redundant questions.
Experimenting is free and is a great way to learn things.