When fasting for kafaarat al-yameen, the three days do not have to be consecutive. If you fast them separately, that is sufficient, because of the general meaning of the verse in which Allaah says (interpretation of the meaning):
“Allaah will not punish you for what is unintentional in your oaths, but He will punish you for your deliberate oaths; for its expiation (a deliberate oath) feed ten Masaakeen (poor persons), on a scale of the average of that with which you feed your own families, or clothe them or manumit a slave. But whosoever cannot afford (that), then he should fast for three days…”
Allaah did not stipulate that they must be consecutive.
Ibn Hazm said in al-Muhalla (6/345):
It is sufficient to fast the three days separately, if one wishes – which is the view of Maalik and al-Shaafa’i – because Allaah did not stipulate whether they should be consecutive or separate. So however a person fasts them is sufficient.
And it says in Fataawa al-Lajnah al-Daa’imah (23/22):
It is better if the fasts for kafaarat al-yameen are done consecutively, but if they are not, then there is nothing wrong with that.
See al-Insaaf, 11/42 , Al-Mughni, 10/15 , Al-Mudawwanah, 1/280.