Magnesium oxide is the worse, so do not get that one. Basically anyone that ends in “ate” in fine. For example “citrate”.
You inquired how much to take with 2000iu of Vitamin D. Just so you know, we recommend adults take 5000iu a day. If you tested deficient, then you should really take a higher amount than that for a minimum 8 weeks. If you already have a health condition or weigh more than 150lbs, you probably also need to take more.