You need a fork which is designed for a 29 inch wheel, be Boost spaced, and has between 150mm and 160mm of travel. You can put a bigger travel fork on it but unless you are getting seriously rad on the bike then no point, as it will throw off the geometry for normal riding.
And I think you mean Fox 34?
The forks you will probably be looking at IF LOOKING AT fox forks are either a Fox 34 or 36, the number realties to the diameter of the fork stanchions, the 36's are a burlier for designed for more aggressive/enduro riding, whereas the 34's are a trail fork. within each range there are different levels of fork, factory being the top spec.
With Rockshox you are going to be looking at either a Revelation/Pike or a Yari/Lyric, the revelation/pike being their equivalent of a 34, and the Yari/Lyric their equivalent of a 36.
Unlike Fox the Rockshox forks tend to have a different name rather than be part of a specific range, so whilst with Fox you have the 36 Elite and Factory, with Rockshox you have the Yari, which is the cheaper version of the Lyric.
These links should help explain the fork ranges:
Your complete guide to the Fox Shox fork range
Your complete guide to the RockShox fork range