rar to ciso conversion can actually mean two things, with the one most obvious being just extracting .ciso image from RAR archive, in which case using WinRAR or something like that solves the problem.
Another way how to look on this would be to actually produce a Wii compressed game image, based on content stored within RAR archive, possibly a rip or backup. In this case you have to use some specialized software utility, such as the Wii Backup Manager.
Updated: July 25, 2023