Much like any other modern compressed archives even 7zip archives can be split to pieces in so called multi-volume archives. When needed, these pieces can be merged back to a single archive using any utility that supports 7zip formats.You may even change the compression method from 7zip to RAR should you want it.
Convert Split Multi-volume 7-ZIP compressed file archive (part 1) to WinRAR RAR compressed archive.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert 7z.001 to rar on Windows
Popular open source file archiver with a high compression ratio
Convert from 7z.001 file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.