MDBox -> maildir format conversion - delete old storage/keep old files removal

After a few conversion over time we noticed we had a mixed enviroment on our cPanel server. To handle better recovery we wanted to move all mailboxes to maildir format. We started "Mailbox Conversion",choose to "Convert to maildir", selected the users and selected "Keep old mailbox files". Everything went fine and now all the mailboxes are in maildir format. My question: How do I remove/delete all the old mdbox formatted files because we selected "Keep old mailbox files"? Is there a cPanel script or 3rth-party script that cleans the server from that old format?