This is simple and easy task. Simply login to your kerio mail account and export your emails to local machine system or any storage media device. All the emails of Kerio backup would be available in .eml format that is standard email format.
Try SoftwareImperial EML converter tool and Export your emails from Kerio to PST for Outlook.
There is option available either one can export or convert Kerio to PST, EML, MSG, HTML, MBOX, NSF, OLM, RTF, Txt and so formats. Or one can also directly import Kerio Backup Emails into the program SoftwareImperial EML converter and select Outlook.com, Gmail, yahoo, Exchange Server, iCloud, Zimbra, IBM notes, Zoho, Godaddy, Amazon workmail and to any imap account.