Hello @Harriann, good to see you keep visiting the Fitbit Community! Whne you upgrade your mobile devices and this is listed as compatible, there is no need to re-pair your tracker; as it is on your account already. So is just matter to log in to your Fitbit app on your new phone to sync your information.
However If you are experiencing issues to sync, try to use the recommendation from the following post: Having trouble syncing? (here's how to fix this).
If the issue keep persisting, try to set your tracker again. (Do not remove your tracker from your account before you go with this process) The following post will give you the instructions for the Android process.
See you around and hope this helps.
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