[z3n]

Did you go to “import” (or import from another browser) option under file menu?
You might have to browse to the saved location of the files when prompted

[TangoLimaSierra]

If you use the sync option in Firefox everything will come back when you load it on another PC. Nice feature

In Thunder bird export to a USB or folder on your PC. Import the file on the new one.

Just reloaded my computer yesterday and both functions worked great.

[kiryandil]

I couldn’t even install Thunderbird on my Windows 11 machine.

[Lee N. Field]

I've been using a Windows 7 laptop. I recently bought a Windows 11 laptop.

I moved the AppData/Roaming/Thunderchicken/Profiles folder, and the AppData/Roaming/Mozilla/Firefox/Profiles folder to a hard drive, then moved them onto the new laptop, copying over the old folders in that location.

What I do is: 1)run Firefox and Thunderbird once, to let it set up the appdata folders. 2)delete the contents of the new Profiles folder. 3)paste the contents of the old Profiles folders into the new, now empty, profiles folders.

[FRactional]

You might want to try MozBackup 1.5.1 Backup/Restore freeware for multiple Mozilla products. It’s 12 years old, but still seems to work fine on my Win11 desktop to save occasional backups for FireFox 130.0 (64-bit) and Thunderbird 115.15.0 (64-bit).

I have used it in the past to transfer profiles from an old computer to a new new computer and “restore” them to new FF and TB installs.

YMMV

https://mozbackup.jasnapaka.com/

[daniel1212]

A back up program such as Macrium Reflect FREE Edition Choose free (for personal, noncommercial use) should be able to back up files and restore them where you want.