Update Old .NET Desktop Application

ONLY FREELANCERS NO COMAPNIES

Hi, I have an old .NET desktop application (around 8–9 years old) which runs as a small EXE and currently uses SQL Server Compact Edition database.
We need to make some modifications:
1) Migrate the existing SQL Server Compact Edition database to a modern database system.
2) Offline-First Architecture with Auto Sync: The application should continue working offline.
When internet is available, backup/offline entries should automatically sync to the main database/server.
3) The software currently has a 1-year expiry key/license system already implemented we need to change few thing here only small changes.
4) some small changes to our exe application.
Please let me know:

Your experience with old .NET WinForms/WPF applications