REGEX: Delete the content of all files that do not contain the word/words

Use the following:

• Ctrl+Shift+F
• Find what: \A(?:(?!\bMIRELA HOME\b).)*\z
• Replace with: LEAVE EMPTY
• Filters: Whatever you want
• Directory: Path\where\your\files\are
• CHECK Match case
• CHECK Regular expression
• CHECK . matches newline
• Replace in Files

Explanation:

\A                  # beginning of file
        # Tempered Greedy Token
    (?:                 # non capture group
        (?!                 # negative lookahead
            \b                  # word boundary
            MIRELA HOME         # string to find
            \b                  # word boundary
        )                   # end lookahead
        .                   # any character
    )*                  # end group, mayy appear 0 or more times
\z                  # end of file