You need to download a appropriate version of software (PC or MAC)
Install the software and connect your blackberry 7 device with it, this will show a warning after connecting but just ignore that and continue your work
Then click on TRANSFER DEVICE DATA and then click on Next ,
Your data transfer process will be started and all you data will be saved to your PC till further instructions.
After the transfer is finished it will ask you to connect your new blackberry 10 device and then you can disconnect and again connect your new device.
When you will connect your device it will show you some instruction message, you can click on Next to continue.
You data transfer will be started from your system to blackberry device.