The blueprint interface allows the BPSC_LPSP_Inventory component to access properties on its owners. These properties are a very important requirement, which is why the owner should have all of them.
If you seek to access the BPI_LPSP_Inventory_Target, it is conveniently located at the following path: InfimaGames/LowPolyShooterPack/Core/Inventory/BPI_LPSP_Inventory_Target.