a typical 4.0 website will be a solution, which one or more projects. each project produces a dll named after the project. so in your case deliver.dll and deliver.website.dll probably resent two different user projects. DataModel is probably a user project.
a 4.0 website generates several dlls depending on the style. if source incudes, then the page.aspx and its code behind are shipped with the site. if code behind style the page.aspx is shipped, but the code behind and the designer files are built into one dll. the designer files are partial classes,
also a project may reference 3rd party dll's and system.dll's.
the Telerik.* dlls are third party. they were probably added to the project a nuget packages. but you can start out as just binary references in the project.
the system dlls will need to be added as project references. the Microsoft one typically start with Microsoft. or system.
hint: your first goal is to determine which dll is the websites dll. this dll will have all the code behind and app code. when you decompile instead of seperate page files and designer files you will get one source file. you should create a small test site in the style of the your site. build and decompile to see how stuff is put together.
it will be quite a bit of work to get the site to work with visual studio if code behind and designer files were used.