You can do this conversion in the query itself. I have done it in SQL Server sometime back. Below is a query sample which you can use in your scenario to do in UiPath.
DECLARE @Amount DEC(18,2)
SET @Amount = 1025040.23
select [Standard] = cast(format(@Amount, 'N', 'en-US') as varchar(20))
The output of this is: 1,025,040.23
If its in MySQL Use below SELECT FORMAT(1235332.1,4);
If this works out for you, please mark the answer as the solution so anyone seeking for such solutions to be done using Uipath will also benefit from it