i connect the drive again it ask me to format the drive i have formated how can i reach my Files .
You will have to treat this much the same way as having formatted a drive in Windows that had data on it.
If you've done a Quick Format you have a chance.*
Unmount the drive from the guest, and make some manner of backup - ideally use zfs send/recv to ship the ZVOL contents to another pool for safety, but if you have no second drive or pool available in FreeNAS, take a snapshot of the ZVOL so that you won't accidentally overwrite anything (worse than it is) - then mount the drive again (read-only, if possible)
CRUCIAL - DO NOT IGNORE THIS STEP.
Get a second physical disk (USB is okay) and connect it to your Windows machine.
Save recovered files here. Do not write them back to the iSCSI drive, or you will write into "free space" and potentially clobber any existing data.
we now return to your regularly scheduled program
Use something like TestDisk, PhotoRec, or Recuva to attempt to find/recover the files. Again,
save them to the additional, external/USB drive on your Windows machine. For Badger's sake, don't write back to the iSCSI drive.
*With this said - FreeNAS supports UNMAP/TRIM for iSCSI devices. Some or even all of the data may already be gone, depending on how speedy your system is, if your system detected the iSCSI device as supporting TRIM, and if Windows decided to send TRIMs after a quick format.