I agree with
@B_9710: they are all correct, but again the two which he mentioned have too many trailing 0s on the end, so it looks like you're expressing it to more significant figures than you are. That's a tiny detail, though, and you shouldn't worry too much about it, but it's good practice to avoid excess 0s after the decimal point and after the stated significant figures.
Here are some bounds questions (remember, bounds are the highest and lowest numbers that would round to the given number at its given accuracy).
1) Find the upper and lower bounds of the following:
a) 350, which has been rounded to
2sf (note: 347 = 350 to 2 sf)
b) 350, which has been rounded to
3sf (note: 347 this time = 347 to 3 sf, not 350)
c) 350.0, which has been rounded to 1 decimal place.
2) A calculator is 16cm long, to the nearest cm. What are the upper and lower bounds of its length?
3) A cube has side lengths 30cm, to 2 sig figs. What is the maximum possible volume of the box?