Sorry, try reading this thread (and the linked pages)
viewtopic.php?f=17&t=1863In short - your PokerTracker3 stors iot's information in a PostgreSQL database. This database is unreadable to a normal person.
If you want to make a backup, you must use the pg_dump (or pg_dumpall) utility, then save the result elsewhere while you format.
Alternatively, you can export the hand history files using PT3's export function, or simply keep the HH files you import in a safe location - then after format, rebuild the database from those HH files.
It would be far quicker to dump//restore the database files, however.