How to compare two columns and find out the missing elements in one with respect to other

I have two Columns data


first column name is "Items Recieved" it contains 25000 values.
second column contains "Delivered Items" it contains 22000 values which are derived from above 2500 recieved values.
remaining 3000 values are Un-Delivered Items.

I want to fetch the data of these 3000 items. in third columns. please any idea ?