There is only one power pass though port per splitter it is possible that you may have more then one splitter if you can follow the coax from the dish it will take you to the splitter/power inserter and yes the power inserter can be before the splitter but that is not the usual way to install it.
Any unused ports should be terminated even the power pass though port and you can use that port to connect to a receiver when not used for power.
