I think you might be mistaken. Firefox sync (the sync integrated into firefox) is not the same service as Google sync. You cannot provide either one with the credentials for the other as they do not share data with each other.

i know and i use Firefox Sync not Google

Firefox Sync just had a major overhaul between version 30 and 31 if you havent migrated to the new firefox sync please follow these steps to migrate to the new firefox sync.

I think I did not explain the problem correctly , i don't have 2 device , i make sync and now i re-install windows for the device and need to restore sync from my old firefox .

From what you've described you have very limited options. To get access to your old user data you must install a version of firefox less than 31 29 (I was incorrect as stated below it was firefox 28-29 that change happened not 30-31) with the old sync functionality as well as have your secret key for that account to do a login based recovery. once you have done that you must update to the latest firefox version and unlink the old firefox sync account and create a new account with firefox sync. when you sign into your new account all your old data will be migrated to the new account. If you are missing your secret key than you have no way of recovering that data and you must create a new firefox sync account and start from scratch.

Yasser,

If you change your Password for your Sync account, your data on the Sync server will be deleted.

To begin with, it sounds like you used Sync for the wrong reason. Sync isn't intended as a backup media, it was made to synchronize Firefox data between multiple devices.

deleted some content Firefox 28 was the last version that used the Sync Key ["secret key"] - aka Recovery Key and did "Pairing" for connecting additional or formatted / OS reinstalled devices.

Firefox 29+ uses only the email address for your Sync account username and a Password. The "Key" is now a hidden implementation, the user never needs to deal with it.

Which version of Firefox were you using prior to re-installing Windows?

If you were using Firefox 28 or earlier, you're going to have to install Firefox 28 to even stand a chance of recovering your data using the older version of Sync. To connect to Sync you're going to need your Recovery Key, along with your Username (email addy) and the correct Password.

But if you have already requested a new password for your Sync account, your data has probably been deleted. So would probably be wasting your time.