Can I do connection between Rotary Encoder with PLC without use any External Counter in the machine , to measure the length by cm or mm ?

Its's not difficult; How to do it depends on the PLC you are using and what speed the encoder is rotating at. The PLC must cycle fast enough to reliably count all the pulses.

My team uses them all the time to measure belt travel. In our case it works out to about one pulse per linear inch. We use a wheel giving5 pulses per rotation, but we use both channel A and channel B so we actually have10 pulses per rotation. The encoder is wired directly to a DC input card. No high speed module is required in our case. An application with high RPM and many pulses per rotation may require one and most PLC's have high speed counters that will take the pulses from the A and B channels of the encoder. It will increment or decrements the count depending on which way the shaft is rotating.

Yes ofcouse, you can connect rotary encoder with PLC directly. You must have Pulse input module in PLC Rack for this purpose. Distance covered/pulse by rotary encoder is mentioned in its manual, so you can calculate its distance.