The concept of a .DAT file is considered rather generic. In other words, there's no standard related to what a .DAT file contains or what it's structure should look like. The contents and structure are governed by whatever application created/uses the .DAT file. So you need to determine what the target application expects, in terms of the .DAT file, and then you can work on converting the .CSV.
As
@Kirtish Trivedi mentioned, it could be as easy as just changing the file extension, or it could involve needing to perform a significant reorganization of the data contained in the .CSV.
Cheers,
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Eric Wilson
Director, Integrations and Enablement
Blue Prism Digital Exchange
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