I did it.
Download all 4 parts in one folder. Then combine them all into one .7z file.
I used ubuntu. I opened a terminal in the folder with the files and typed-
$ 7z e 740f98e1a560e118a04ff356.7z.001 -tsplit
It created single .7z file. I renamed it to john.7z.
Then I extracted it using
$ 7za x john.7z
It will ask for password. Use this Password : hacksnation.com/u/Robert_California
DONE!
