I have client -server(window application) solution for Pacs can i convert it to web based paces???

A PACS system needs to be online to start with, obviously. If you have your source code, and you have a clear idea of how you want a PACS server to run on your server, and then send information down to a web client, there's no reason why you can't do this. Having said that, if you need to ask, it's probable you don't know enough about ASP.NET to do it. You need to write the ASP.NET portion completely, and understand the windows app code well enough to use the code, or rewrite it.