How do I coverte rar files to mp3?

Which service offers rar music files?

RAR isn't a music format. It's a compressed file with files INSIDE it, like ZIP files. You need to download a RAR tool to open the compressed file.

WINZIP does it, opens both ZIP files and RAR files. Or, Win-RAR does the same thing.

WinRAR download and support
WinZip® - Select a Product Download

WinZip isn't free, but many home users never "buy" a license since it works anyway. Your call.