Samsung abandoned firmware updates for Galaxy Tab 2 10.1 but that has not stopped XDA from releasing continuous updates. Android 5 lollipop update for the Samsung Galaxy Tab 2 10.1 is now available for download. This ROM is compatible with both P5100 and P5110 (wifi only and 3G versions).
Download the Rom for your device from here and copy to your tablet.
Reboot into Recovery
Wipe Data Factory Reset
Format /system (Recommend, but make sure you placed your files on your Micro SD Card. Your internal storage get formatted).
Format /data (better "format /data and /data/media").
Flash Rom and 5.0.x GApps (download link).
Flash Super Su (download supersu from here).