Hi Shivam,
You can refer the below sample test case to achive your requirment
1. Use the "Load a Set of File Names" Data Set to read *.dat file names from the directory
2."Read a Fille (Disk, URL or Classpath) step " to load the file content and store it in a property "msgcontent"
3. Use the property name {{msgcontent}} in the IBM mq step Contents Section
Regards,
Balamurugan.