I presume that the files you have are named something like 126421.M826736P29173V0000805I028D001B_1.servername.domain.com,S=31796:2,S ?
Copy (ie, FTP) them to the folder username/mail/domain.com/user/cur/ (or /home/username/mail/domain.com/user/cur/ if logged in as root)
*username* will be your cPanel account name
*domain.com* is the second half of your email address
*user* is the first half of your email address
When next you download mail via POP3 or IMAP or you log into webmail, you'll see your email.