There are several round "holes" in our stone masonry foundation
presumably from old pipes that have been subsequently removed. The
holes are about 2 inches in diameter and extend through the foundation
just below the level of the sill.

I would like to fill in these holes but was wondering what is
best/easiest?

Do I mix my own concrete? (if so, what type?)
Is there a good patching premix?
Any other suggestions?