ANSWER:
It is totally prohibited to fast on the 10th of dhul hijja as it’s the Eid day and it’s forbidden to fast on the two Eids and the days of tashreek (11, 12 and 13th dhul hijja)
9th of dhul hijja is the day of arafa and it’s highly recommended to fast this day for the non hajis and you can have double intention of fasting the missed day and the day of arafa.