Build Failure when scanning the project with sonar cloud

[MarkLee131]

Hi, I am trying to scan the project's source code with the Sonar Cloud by forking the project to my repo.

But, when I used dotnet build, I encountered the build failure, and I checked the log, getting the error like the following:
error MSB3644: The reference assemblies for .NETFramework,Version=v3.5 were not found. To resolve this, install the Developer Pack (SDK/Targeting Pack) for this framework version or retarget your application.

I am fresh in the dotnet project, so I don't know how to fix it.
Is it an issue about the environment, i.e., Sonar Cloud? Or is it caused by the reason that this project is out of date?

Thank!