I want to get all my notes back, they are all gone from my Firefox account. I know that there was a sync between my old phone and Firefox account, but when I got a new phone in my hands, my notes have gone from my Firefox account.
Hello and welcome to the Mozilla Discourse forums.
From your question, I think you may have been using your Firefox Account as an online backup. This is not what a Firefox Account does or how Notes works.
When you Sync bookmarks or save a Note, that data is sent off to the other Firefox installation you may have connected to your account. There is no permanent storage online. It sometimes happens that you can reinstall a copy of Firefox quickly and pick up the same synced data, but that is not guaranteed.
I am very sorry, but unless you have those Notes saved on another copy of Firefox, I do not believe that there is any way to get them back.
I try to do backup of my AppData in PC so I might have old profile where (I suppose) I had some notes synced. How can I restore notes from old user profile, is it even possible?