It might be possible that you can convert or re-save older CAMREC files to newer TREC format if you own one of the later Camtasia Studio versions that support TREC format. . Other than that, there is probably no way to perform this conversion as both this file types are exclusive to Camtasia.
Convert Camtasia Studio video recording (version 8.3 or earlier) to Camtasia Studio recorded session.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert camrec to trec on Windows
A screen capture and video editing software
Convert from camrec 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.