> I am not even sure which trinity version I have installed but it must be
> a couple of years old (still running Kubuntu 10.04). I would like to
> purge it before try to install 3.5.13

A graphical way:
Open the Control Center, it should appear there (at least it does in pre-v14.0.0, but I assume it is something that was always there from the KDE days).
Or open the "About Trinity" from the help menu of Konqueror/Konsole/....

Cheers
  Michele