first, thanks in advance for any help. I searched through as many threads to see if this was already answered, but no luck.

I have a list of values in column A :

apple
plum
orange
melon
apple
apple
orange
banana


In other sheet there is other list ( column B) :

plum
apple
strawberry
peach


I want to know how many unique values are in column A that are present in column B:
So the result of formula should be : 2
( apple, plum )