It doesn't seem to be possible to convert CAMPROJ files to TREC format in any program except Camtasia. They are both recordings more or less and the only way to make a TREC one would be to re-create the recording saved in CAMPROJ. But both CAMPROJ and TREC files should be openable in Camtasia and could be exported to some common format like MP4.
Convert Camtasia Studio project to Camtasia Studio recorded session.
We found one software available in the database for this conversion.
Microsoft Windows software - convert camproj to trec on Windows
A screen capture and video editing software
Convert from camproj file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.