Only backup files created from devices running BlackBerry Device Software 5.0 and later can be restored to the BlackBerry 10 smartphone.
I believe the highest OS on the 8700 is 4.5.
you might try reading the backup using an IPD reader to possibly move the data to another format that can be used.
KB33526-How to backup and restore data on the BlackBerry 10 smartphone using BlackBerry Link