So if you have loaded the three Excel tables, you have three tables in QV, not linked to each other, because they don't share a common field name, right?
If your fields are not in the same table, it is probably best to separate these tables, looking at your sample above I might think you have one table with three fields, one record has entries in fields called 'Table A', 'Table B', 'Table C' (or in other words, value x1 in field Table A in in the same record as value y1 in field 'Table B'.
Or maybe this is what you want to show?
I haven't fully understood which values of your table A and B you want to add to Table C, or how your final data model should look like. Could you post your expected outcome?