Thanks for the correction Kathy, I don't know why I said individual units,Not that it really matters, but IU means "international unit".
Here is a site that converts IU to mg or mcg.
https://mypharmatools.com/othertools/iu
Edited to add:
So I looked it up and 1000 IU of Vitamin D = 25 mcg (micrograms) = 0.025 mg
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I never have been keen on the units of measure for drugs.

I never realized when I rescued my little friends it would of helped to have a degree in science! LOL