The ordinary 842E encoders are an EtherNet/IP networked absolute encoder and work as an I/O device.
The 842E-CM versions actually work as Logix Integrated Motion devices and use the motion control instruction set.
With the ordinary one, you have the Position value right there in the Input tags associated with the encoder.
This seems like a very straightforward linear scaling application. The onboard "Enable Scaling" feature might even allow you to do the conversion to inches right in the encoder, without any ladder logic.