✅ Need assistance compiling an older dotnet app

Build FAILED.
Loki.csproj : error NU1100: Unable to resolve 'DotNetProjects.Extended.Wpf.Toolkit (>= 4.6.96)' for '.NETCoreApp,Version=v3.1'.
Loki.csproj : error NU1100: Unable to resolve 'GitVersion.MsBuild (>= 5.6.6)' for '.NETCoreApp,Version=v3.1'.
Loki.csproj : error NU1100: Unable to resolve 'gong-wpf-dragdrop (>= 2.3.2)' for '.NETCoreApp,Version=v3.1'.
Loki.csproj : error NU1100: Unable to resolve 'JetBrains.Annotations (>= 2020.3.0)' for '.NETCoreApp,Version=v3.1'.
    0 Warning(s)
    4 Error(s)