One of the embuggerances of much long distance flying is that transition levels seem to be treated as state secrets. However, clearly in that neck of thr woods it is above 5000ft, and presumably below 6500. In general it is easiest to be lazy and assume that the controller knows where it is and take your queue from the clearances you are given. The units used on charts to define top and bottom of CAS can also be a useful clue.
G