I found the solution. We can add all the xaps to zip file and create a manifest.xml file (below) which we add to the root of our zip and then upload the zip file.
eg:
<SilverlightApp>
<source>Loader.xap</source>
<width>600</width>
<height>400</height>
<jsOrder />
</SilverlightApp>
Thanks Tim Heuer for assisting me.