Problem with ros melodic and gazebo 9

[nicohdd]

hello, I would like to solve my problem, i to try install a plugin to gazebo but when I write the make comand on my terminal, show this erro:

/home/matheus/catkin_ws/bluerov_simulation/freebuoyancy_gazebo/src/freebuoyancy.cpp:13:10: fatal error: gazebo/math/Pose.hh: No such file or directory
#include <gazebo/math/Pose.hh>

this is the plungin link:

https://gist.githubusercontent.com/monabf/bc04b7ab366f812c645bf0aa6f22c8de/raw/e8f7d0a9f4bc8add7909722f37416d74f383f811/bluerov2_ardusub_sitl_tutorial.txt
I'm new in gazebo and ros.