Of course there is a way and its easy. Check how these devices work.
Make a little setup on a bench, without the PLC connected to the device. Just like in school ...
You need a power supply
You need a few resistors.
Wire this gizmo so you don't release the embeded smoke and test it.
See, the device is just like a switch. Changing state from OPEN to CLOSE.
You connect the device + and 0V.
If you start from the PSup. and into a 5K resistor (check the device max. am) then enter you NPN cct at the load connection and out to 0V.
Make it activate. Use your DVM and check where the heck the signal is changing. You'll then find where to connect you PLC.
The ONLY way to see how those darn device work (NPN / PNP) is to play with them on the bench at least once.
Then you'll know that you can connect any sink/source device to any PLC inputs. Wathever there type is... But of course, you need not connect 120 V to this