According to the Samsung spec page for your TV, the TV does have an optical digital audio connector. (It doesn't specify whether it's input or output, but it's probably labelled on your unit.)
The optical digital-audio input is what you want to use. You need a cable like these - optical TOSlink to optical TOSlink.
If not, check for analog stereo inputs (a pair of RCA-style inputs, one red, one white). You'd need a cable like these with a 1/8" stereo headphone plug to red & white RCA plugs on the other end. The mini plug goes into your Mac Mini's headphone output, and the RCA plugs go to your TV's analog stereo input. This will not be as high-quality as the optical.
Update: OK, it sounds like this "PC/DVI audio in" is another headphone-style jack like the analog audio output on your Mac Mini. In that case you just need a cable with the 1/8" stereo headphone plugs on both ends (some stores will label these 3.5mm plugs). The cable may look something like this:
Links to shopping sites in this post are for example purposes only. I am not endorsing any store or any product. Links are only provided to show what these cables will look like and how you can identify the correct cable in your store of choice.