I had access to the #karaoke server
Your question is conflicting. What exactly is a channel server?
but I can't find my old server(#realmworld).
Of course, we should know that #realmworld is not a server, but a channel. We know this, because channels start with a #.
How do I get that back and get everything setup the way it was. HELP!
Get your mIRC back? I guess you re-downloaded a plain mIRC and lost your saved settings from your previous mIRC. You'll have to redo them, then. Though if you downloaded some add-ons or scripts to that mIRC, you will have to redownload them too.