"...velocity is I:e.3/I:e.2...is it right?" No.
The rate or velocity is the value in I:e.3 and only I:e.3 as I mentioned in my previous post.
Now if you want to convert it to engineering units "tr/sec" then you need to calculate how many counts of the encoder there are per "tr". I do not know what a "tr" is. To calculate this you need to know the number of encoder counts per revolution of the motor. You also need to know the number of "tr" per revolution of the motor. Then you take "tr" per motor revolution and divide that by the number of counts per motor revolution to get your scale factor, which is a constant. (Note, there are other ways to calculate this. You can look at the number of counts per encoder revolution, the number of motor revolutions per encoder, and the number of "tr" per motor revolution.)
Once you calculate this scale factor, you can calculate in the PLC the velocity in units of "tr/sec". You would do this by taking the value of I:e.3 and dividing it by your scale factor.
So, what does your "tr" represent? I am not familiar with this unit.
What slot is your 1746-HSCE in?