السلام عليكم ورحمه الله وبركاته Ahsan Allahu Ilaikum If a person has some fasts to make up (almost 70 days) as a kaffarah for breaking an oath, is he allowed to fast 6 days of Shawaal and combine the intention?

The best thing to do is that you make up the mandatory fasts that are upon you, and then you would do voluntary fasts, because it might not count. We ask from the bounty of Allah Subhanahu wa Ta'ala that both of them count; however, many of the scholars have said that it does not count. Therefore, your intention must be for making up the obligatory fasts.