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.
You also need to look at the offset of the forks, which is a whole essay in itself to explain, but you should try and get a fork with a similar offset to the one at the moment. You can find the offset of your current forks but typing the serial number (which will be on the back of the fork crown) into this website, it will give you the specs on your current Rockshox Fork, and also give you tuning advice:
I just upgraded my revelation from 150 to 160mm seems good easy fix, haven't hit the bigger jumps yet just small ones in the woods. I was looking at changing the whole fork, fox 36 but a lot of money so thought for £45 quid it was worth an upgrade and try out.
I upgraded my pike on a TL expert to 160mm using an air spring upgrade kit. Cost £39 so a bargain to get that extra 10mm. Makes a different though.
Having said that, I do ride a lot of bike parks and do fairly big jumps so am thinking of getting a lyrik 170mm. I have an Ohlins TTX shock on order for the rear. Then it will be an enduro weapon.