It doesn't matter what format the files are in, they'll concatenate the same way regardless of file type. But I doubt you really want to concatenate several rar files. If you have files named rar1, rar2, etc or something similar then that is a multipart rar file, not a split file that needs concatenating. Any unrar utility should be able to unrar those files together just fine.
The latter is what i meant. Thanks. While i've got your attention. Where would be a good place to start if i were to want to start using terminal. either to be more efficient.. but really just to learn
PS how do you disconnect from a foreign address while in terminal