What should the preposition be before Monday and before Thursday
My mom told me to go to the supermarket in the afternoon from Monday to Thursday
My mom told me to go to the supermarket in the afternoon on Monday to Thursday
I can't tell what your mama is trying to get you to do. :) Does she want you to go to the market every afternoon from Monday to Thursday? In other words, show up Monday afternoon, Tuesday afternoon, Wednesday afternoon, and Thursday afternoon? Or is she saying that the best time to go to the market is any afternoon as long as it's NOT Friday, Saturday or Sunday? Does she want this to be your regular practice, or is it something she is assigning for this week only?
None of the prepositions you have used are incorrect, but the meaning isn't clear.