Help with Item Entity NBT

So I want to execute a procedure at an item entity of a certain kind, but as far as I can tell that requires using the "Item" NBT tag which doesn't appear to functioning very intuitively. I tried a few things, but I can't get the ID tag to work. Maybe because it is weirdly inside of the item NBT tag? I don't know. I even tried just copy-pasting all of the "Item" NBT as it appears in /data with the curly brackets and Count: 1b which I don't even want involved but it didn't work. Does anyone know how to do this or is it impossible? I am open to using code.