can you please explain this bunny,net i think its good it will only charge me when some one download the files other wise it will not charge me
You get charged a fixed fee of $0.01/GB every month for storing files, but there is a $1 minimum.
So if you store 200GB, you pay $2 per month. If you only store 1GB, you still pay the minimum $1.
But keep in mind, you can also choose to have those files stored at multiple locations around the globe, so if you optionally select 4 locations you'll multiply the storage of each file by 4. Depending upon the nature of your business, that might make sense because if your web server is in the UK (for example) but your primary customers are in the US, you can have the files stored closer to those customers, among other locations. Or for the sake of cost, regardless of where your customers are you could just choose the cheapest Volume plan and choose the cheapest data center location.
So that's your fixed storage cost.
That's why I asked when you said 200gb if it was GB or Gb, because depending upon what you're looking to do it might be better off to find a service provider that offers unlimited bandwidth and storage; however, most web hosts that offer that also specifically forbid using services for anything other than a website and so that'd be a gray area I suppose - I'm not sure anybody really checks though.
Then you'd pay $0.005/GB (or less depending upon the country) for the actual bandwidth used.
Essentially, what you're buying is hard drive space for your files on a per GB basis and then you create a "pull zone" that creates a subdomain where those files can be downloaded from by visitors. You could optionally set this up as a CNAME.
There is CDN integration with WordPress via a plugin, but I honestly don't know the limitations. They might not download those files automatically if they're not standard files (.jpg, .css, .etc), so if that's the case you could upload them directly to Bunny.net or I believe there may be a third party plugin that ties the WordPress media library to Bunny.net but last time I used it I decided against it - I just don't remember why.