Migrate Legacy Rental SQL Database

I have a legacy self-storage rental program that still runs perfectly on an old Windows 7 PC. I’m upgrading to Windows 11 and need the full history that lives in its SQL database to come across intact.

The original developer is no longer with us, but he left me a master password and a note saying I must “detach and reattach” the database after restoring a backup. I tried a fresh install of the software on the new PC and loaded the backup, yet the history tables stayed empty—clearly the detach/attach step never happened.

Here’s what I can supply right away:
• an image or installer of the application as it sits on the Windows 7 box
• the working database files in whatever format you direct (MDF/LDF or equivalent)
• remote access to both machines if that speeds things up

What I don’t have:
• any management console that talks to the database
• documentation or schema notes from the original author

I need someone who can:
1. Safely detach the live database from the Windows 7 machine (or a copy of it),
2. Reattach it on the Windows 11 install so the program shows every historic record,
3. Give me a simple, repeatable method or script so I’m not stuck again during future moves or backups.

I’ll consider the job complete when I open the software on Windows 11 and see the same customer and payment history that appears on the old PC. If any SQL Server utilities (e.g., SQL Server Management Studio, sqlcmd, PowerShell, etc.) or alternative tools are required, please let me know and I will install them.