You can look at the M/M/1 Queuing System example in the MathWorks documentation link here.
Further the error "The system cannot find the file specified" could be because of many possibilities,
- Old files interfering with your previously installed MATLAB.
- Check if the MATLAB installation is in the specified directory and if the specified example is in the folder specified.
- It could also be your MATLAB installer is corrupted.
Simple solution would be trying to reinstall MATLAB or develop the example with the help of the documentation from the website.