Um. It's not that simple: a C instruction does not necessarily translate to a single machine (or assembly) instruction - and case in particular is a more complex operation than you might think.
Probably the best place to start is to use Google to find a disassembler for your chosen processor (you don't specify it, and assembly is processor or processor family specific unlike C) and look at what that compiles to.
However, if you don't "know assembler" then it probably won't help much.
At a minimum, you may find that your C compiler supports something like
which allows you to include assembly code in your C source file - obviating the need for a separate assembler for small tasks.