You can use the ROS xacro utility to convert your XACRO files to URDF before importing into MATLAB.
In a ROS enabled terminal, you can enter the following command, replacing the paths and names for your input and output files:
rosrun xacro xacro --inorder -o ~/myfile.urdf ~/myfile.xacro
You can then check the generated file to see if it's valid
check_urdf ~/myfile.urdf
If this step is successful, you can copy the URDF file and its dependent meshes somewhere accessible by MATLAB. Then, you can try import your robot as follows
>> robot = importrobot('myfile.urdf');
- Sebastian