Use 7-zip, or compatible compression utilities to unpack .001 multi-volume archive and extracted data again add to 7z compressed archive. To unpack .001 file you will also need all parts of a multi-volume archive.
Convert Compressed file from a multi-volume archive (part 1) to 7-ZIP compressed 7z archive.
We have found 6 software records in our database eligible for .001 to .7z file format conversion.
Microsoft Windows software - convert 001 to 7z on Windows
Popular open source file archiver with a high compression ratio
Convert from 001 file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned 001 to 7z. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
One of the oldest and most popular shareware file archiver and data compression utility
A free open source archive utility
Apple macOS / Mac OS X software - convert 001 to 7z on OS X
Mac version of the popular utility
A backup and archive utility
Linux/Unix software - convert 001 to 7z on Linux
A Linux application used as frontend for popular compression tools