Decode a Base64 encoded file format to display original content in Appian

Hi All,

We have an integration with O356 using Graph API.  Using this we are sending and receiving attachments from/to Appian. While storing the user response and it's attachment into Appian we are getting the Base64 encoded data files which is not in original data readable format. 

Please do let us know the approach to decode these encoded files appropriately while storing in Appian.

Thanks