The conversion procedure is very simple enough. Let us assume /dev/sda6 (ext2 now) mounted on /convert. You will be seeing fstb entries like,
/dev/sda6 /convert ext2 defaults 0 0
Unmount the partition
umount /dev/sda6
Enable Journal (converting to ext3) using tune2fs command,
tune2fs -j /dev/sda6
Edit /etc/fstab and for /dev/sda6 change the file system type to ext3. Finally, the entry should be like this,
/dev/sda6 /convert ext3 defaults 1 2
Mount the partition using mount command,
mount -a
If above command doesn’t work, reboot the system and check.