Load the purchase data into power bi. The data model should be created automatically, but I did have to select ‘use first row as headers’ for the item table:
Create a slicer with Item
Then create a DAX measure that to count the number of items selected on the slicer
Items Selected = DISTINCTCOUNT(items[Item])
I created a card showing the value of Items Selected. Here’s my view… since I have bananas, melon, and papaya selected the view shows 3 items selected.