Hello @WaisAhmadMirwais60647 ,
if they do not support the modern command syntax with bridge domains and service instance I am afraid you cannot bridge over POS interfaces.
Many years ago I used the first forms of IRB to perform bridging between LANs using routers connected with a serial interface but it was using the old syntax of bridge-group.
I performed several type of tests over POS interfaces but I have never tried to configure bridging.
POS is IP packets over SONET/SDH and it was introduced as a great semplification in comparison to ATM interfaces using Sonet/SDH for high speed point to point links with also reduced overhead.
Hope to help