First thing there is no bulk update in sharepoint activitirw as of now
So you need to loop theough your datatable which you want to update to sharepoint then inside that use for eqch list item and filter option in it to get only one list item using any unique column value (or get list items basically would get you a list of listitems which you would have converted to datatable where you can filter and get the list item you have updated) and then use update item inside that by passing the identified list item value to it
The xaml query is used in sharepoint activities which are no more there and in office 365 you can use odata filter to get each item which is the filter i am talkinh about
Cheers