Your original format seems semicolon separated value format. So for now, can you try to set Semicolon at Delimiter property in WriteCSV, as the following?
You can use read range activity to get the data in excel to datatable. Then use output datatable to convert datatable to string. Then use replace method to repalce the “,”.
YOURSTRING.REPLACE(“,”,“.”)
Then use text to datatable activity to convert back to datatable.