: Use a compatible archiver like 7-Zip, PeaZip , or WinZip to open only the first file in the sequence ( .001 ).
: Ensure you have every preceding part in the same folder (e.g., a2860.7z.001 through a2860.7z.011 ). a2860.7z.011
Are you of the sequence, or are you getting an error message when trying to open the first volume? How to open 011 file (and what it is) - File.org : Use a compatible archiver like 7-Zip, PeaZip