You're asking multiple questions, each of which should probably be their own StackOverflow post.
Do we have to convert SCORM packages to Tin Can if we want to launch SCORM courses via a desktop app?
How do you import/handle SCORM packages in Tin Can?
Assuming the SCORM course has been converted to Tin Can, how do you launch Tin Can courses in a desktop environment?
The answer to question #1 is no. SCORM is designed to run in a browser environment and requires JavaScript, but this can be provided on the desktop in a number of ways. I'd check .Net threads for solutions specific to .Net
Question #2 is not easy to answer unless you use a 3rd-party solution like Rustici Software's SCORM Driver. Even then, you will need to figure out how to ingest and parse the SCORM manifests. If the SCORM package is a single-SCO course with a simple manifest, you will only need to worry about converting SCORM run-time (JavaScript) calls from SCORM to Tin Can. If the SCORM package is a multi-SCO course, or makes use of features in the manifest such as global objects or sequencing rules, you will have a much more difficult time sorting it all out. This is true whether you use Tin Can or not. This is a good starting point (grab a cup of coffee first). https://github.com/adlnet/xAPI-SCORM-Profile/blob/master/xapi-scorm-profile.md
For question #3: There are many tutorials for Tin Can online -- unlike SCORM, Tin Can is not specific to a browser, and doesn't require JavaScript. You can use any system that supports REST calls.