Your original post suggested to me that you wanted to replace abc followed by any number with abc123.
If you want to replace any multi-letter sequence that precedes a multi-digit sequence, you could use:
Find = <[A-Za-z]{1,}[0-9]{1,}>
Replace = '^&'
to insert the single-quote characters either side

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]