How to obtain Peak and Average Power in Radar Detection?
The classic radar range equation can be used to solve this problem. Just google "radar range equation" if you are not familiar with it (although you should be if you are asking this question).  All of the information given in your question can be used to deduce the variables in the range equation, one of which is your unknown, the peak power. Once the peak power is known the average power can be calculated from it, the pulse repetition rate and the pulse width.