You are using c code in a Rmarkdown chunk. This is note standard usage, so not easy for first time with RStudio IDE.
You need to be sure your compiling environment is setup. On WINDOWS, it is not easy to use c code output of the box.
It seems here you are missing a dll file.
Not really an R error, so don't really know how to solve. The dll should be written in the current directory when compilling.
Can't you get help from your course's teacher or assistant ? Or even other student ?
I would advice to at least use RStudio Projects (top right of your windows is currently none) to work on your projects.