Hey there
First thing, please take a look at and try to adhere to the Unreal coding standards Coding Standard | Unreal Engine 4.27 Documentation
This makes it easier when you’re asking questions for other developers (like me) to understand your code and help you quicker.
As far as what you need to do for the code, you’ve got it all set up mostly correct, but you’re binding to this, which is an object of type AInventory. You need to get an AInventory_manager object, whose specified function can be bound to the delegate you are doing so with.