Hmm, if you signed into your account on someone else's existing installation of Firefox, you might have gotten some data mixed together. To see what is in the Sync cloud for your account, after signing in, install this add-on:

https://addons.mozilla.org/firefox/addon/about-sync/

After that is installed, you can type or paste about:sync in the address bar and press Enter to load a page showing what is stored. Under each category, the Records (table) or Records (object) mini-tab lets you see the data in more detail.

Is your old data there?

Regarding your backup, did it have your Firefox data folder(s) (profile folders)? Those would have been along a hidden path, so you usually need to set Windows to show hidden files before you can explore.

https://support.microsoft.com/en-us/windows/view-hidden-files-and-folders-in-windows-97fbc472-c603-9d90-91d0-1166d1d9f4b5

And then in your backup, it would have been wherever you see this:

C:\Users\<your-username>\AppData\Roaming\Mozilla\Firefox\Profiles

If you have files there, then you can rescue important data. The following article has the general outline, but let us know if you have specific questions:

Recovering important data from an old profile

Yes it looks like my bookmarks are there in the about:sync I don't speak programming language though. Is there an easy way to retrieve them from about:sync please?

I have found them!! They were there all along but I didn't have the correct Bookmarks button on the toolbar! Yay!