What is the command to know my PulseAudio version?

pulseaudio --version

This should give you an output something like this:

pulseaudio 0.9.21-63-gd3efa-dirty

To get the version of the Debian package you have installed, use:

dpkg -l pulseaudio

which will give output like this:

||/ Name             Version          Description
+++-================-================-================================================
ii  pulseaudio       1:0.9.22~0.9.21+ PulseAudio sound server