If you do not recognize the "YO342" project code, check the source or the directory where you found it for a .txt or .nfo file, which usually contains a description of the archive's contents.
Always initiate the extraction by right-clicking on part01.rar . The software will automatically pull data from part08 during the process. YO342.part08.rar
If part08 is the final part, it is often smaller than the others. If any part is missing or corrupted, the extraction will fail. If you do not recognize the "YO342" project