Simple. You need to be in the same directory as the source code file to run make.
The screen shot shows that you're in the root directory. You need to switch to the directory containing the source code file.
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The psets have been rearranged a bit. The c programs that used to run through pset 5 are now psets 1 through 4, so yes, some shuffling has occurred. Speller is definitely pset4 now.
I would suggest that you move all your completed work to an archive directory, put your in-progress work on Speller in a new pset4 directiry and proceed from there.
Your username in the Terminal shell is ubuntu. This is true for everyone, regardless of what your Cloud 9 IDE username is.
Have you tried typing ls to list the contents of your home directory? It should return a list of folders, something like: