@Daniyal_Tahir
If you’re using a regular DataTable, then you don’t need to use Fetch(…) or ExpansionFieldOption. Those are mainly used with data from Data Service or other sources where relationships need to be expanded.
In your case, since your DataTable contains columns like "Country", "D.O.B", and "Full Name", you only need to pass the DataTable variable itself in the “List Source”. Then, in the Column field, enter the exact column name from which you want to display values, such as “Full Name”.