Truck still skipping

I took it to a mechanic and he told me to come get it after having it for 2 weeks. Said to take it to someone else bc he didn’t know what is wrong with it.
Can some one please explain to me how to check the wire and ecm or pcm with the meter I have. I put pic of it on here. It showed code p0356 and I have changed coil 2 times and spark plug 2 times.
I’m don’t know much about wiring or a meter but if it is explained I hopefully can do it

 

P0356 means the PCM is not receiving an ignition confirmation (IGF) signal from the number 6 ignition coil (drivers side rear), this can be caused by a faulty coil, a bad power or ground to the coil, an open or short in the control (IGT) wire, an open in the ignition confirmation (IGF) wire, or a bad PCM.

The first and simplest test is to swap the coil to a different cylinder and see if the code moves to the other cylinder, if it doesn't the next step is to check power (Black/Red) and ground (White/Black) at the coil with the key on.
If those are good you will need to check wiring integrity on the IGT (Green) and IGF (White/Red) wires between the coil and the PCM.
If that's good you will need an oscilloscope to check the signals.