I found the ropes you're asking about:
Both of these are good ropes, and both would be suitable. They're both braided, which is good, and they're strong enough.
One of them is 200 ft, though, so you'll probably need to cut it (which is easy to do). The other one is 33 ft, which is a good length – long enough for most setups but still not overly long.
Both are fine, really. If you want a slightly thicker rope, get the 12 mm one. The 10 mm one is shorter and cheaper, and it's fine too.
Even if you don't get these exact ones, these are the kind of ropes you should be looking at in general. It should be braided (double-braided or solid-braided), and about 10–16 mm (or 3/8–5/8 inch) in diameter. The material can be polyester (PES) or polypropylene (PP). Some ropes, e.g. static climbing ropes, can also be made of nylon.
Length should be about 5–10 m (or 16–33 ft). For simple setups, 5m (or 16 ft) should be enough. If your setup is more complex, or you're doing it by a tree, for example, you might need 10 m (or 33 ft). Keep in mind that knots take up a lot of rope as well – more than you'd expect. So it's always better to get more rope than necessary.
Cutting a rope is easy. You just cut it, and burn the ends with a lighter to prevent fraying.