Correct, you have to go with silverlight only. Prism is one of the popular MVVM frame work. there no mandatory that you need to use all of these things, You can create your app with out them as well. But Building WPF/Silverlight is advisable.
Strictly speaking, PRISM is not an MVVM framework. Yes, it has some MVVM features, but it is better regarded as an application composition framework. If the OP didn't build his original app with PRISM then he's got a whole host of work in trying to convert it into PRISM.
*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington
Yes we can go with xbap application even i too thought that also.
But my basic requirement of converting this wpf to an web application is that
1) I am connecting centralized sql server with ado.net which have image data type also, so when i connect to the centralized database and fetch the data and also image am getting huge delay on getting the same. I even asked a question on C# discussion forum on the same and they suggested me to go with image storage in physical drive and use web browser control to access the image. And instead of ado.net can use webservices.
But my thought is that if we create an web application and host the application in same server where the data base server exists will solve my problem. Thats the reason i wanted to convert into web application.
2) According to my understanding xbap application is that, when we trigger that it will download the exe to the local desktop through browser and run from local machine. If that is the case once again i hope i will be getting the same issue. If its is not the case i hope xbap would be the right option for me. Please correct my if my understanding is wrong.