When you installed the newer mIRC, your files were backed up to the backup/ dir in your mIRC directory. You can restore them thusly:
- CLOSE mIRC completely
- COPY the files from the backup/ dir, to the main mIRC dir (overwrite existing files when asked)
- RUN mIRC normally
Hopefully, your settings will be back to where they were before you upgraded.
-genius_at_work