FTP is basically the same from platform to platform (the commands and general process). To use jcl on the mainframe to "pull" data from the unix system, check with the unix sysadmins to make sure you can connect to the unix ftp server correctly and have permission to read the directory(ies) where the files to be sent are located.
The best source of sample jcl is your system support people. They can show you exactly which jcl should be used on your system.
Here is a link to the IBM material:http://publibz.boulder.ibm.com/cgi-bin/ ... 0530175427