Centos to Cpanel email migration

Hi. I migrated my client's website from their old hosting company to my reseller hosting. The old hosting company used Centos Web Panel and I use Cpanel. The problem is I can not view/access the old emails. I have the email backup file which I downloaded from the old host before we changed the nameservers. How can I restore the emails? Or how can I extract the emails to work properly from the backup file?