How to keep a backup of olm data file of microsoft office in mac

Hello

I am a new user of mac and need help in keeping a backup file of olm file of microsoft office Outlook.

I bought my macbook pro 3 days back and imported my old mails from .pst file of my windows laptop and now need to keep the backup of olm file of outlook for future use,

Can anybody please help me doing this.

Thanks in Advance