Display Data from External DB

Hello,

Can anyone guide me for below requirement ?

Currently i am having external DB where all data (Contacts) are processed and stored.

In Dynamics 365, Contacts will be stored, but transaction related to contacts, I want to just display thosoe data (Do not want to store it in CRM DB) when user clicks on refresh or fetch Button.

Kindly suggest me appropriate method to achieve the same.

Thanks in Advance

Regards,

Rutul