Your screenshot shows your files
mario1.c are all located in
~/workspace/, while you call
make mario1 in
~/workspace/pset1/, where it cannot find a file representing a possible source for that target. Move your files to where you expect them, this can be done with the mouse via drag+drop, I've had some issues with this kind of manipulation and would recommend using
mv (stands for "move") on the command line instead. To list files in the current directory, you can use
ls command. If that doesn't show a
mario1.c in current directory,
make mario1 wouldn't find one either.
And when you use
submit50, make sure you are in the right directory containing your source files, and that the files are named exactly as specified.