Mozilla doesn't save that key, only the user has it. Take a look at Sync preferences on the desktop version of Firefox where you have that Sync account setup to see your SyncKey.

On desktop version there is no manage option in the sync prefs

The sync key is listed in the Saved Passwords which can be found at https://support.mozilla.com/en-US/kb/Options%20window%20-%20Security%20panel it will be listed as chrome://weave (Mozilla Services Encryption Passphrase) then click the show passwords button to view the sync key.

On desktop version there is no saved password for sync. On the tablet version, there is no saved pwd option

Try this add-on in your Firefox Mobile browser: https://addons.mozilla.org/en-US/mobile/addon/aboutsynckey/

The instructions to retrieve the Sync Key are described in the add-on page.

synckey requires a version of firefox that has not yet been released

Here's a similar add-on that will work in all versions of mobile Firefox: http://limpet.net/key/

hey thanks, that did it, limpet.net/key did the trick

thanks for all the responses