YOu could try using a windows to Mac program called transmac to format and move data back from your pc to your antique Mac.
The powerbook 140 will run system 7, it is black and white only, something like a 25mhz motorola 68030 cpu. I guess old versions of Claris works or word, Mac paint, Superpaint, Lightning Paint etc will run.
Though it is technically possible for this to surf the net via dial up, it would be pretty much unusuable. Maybe email might work
I have seen better laptops given away for free, and for good reason.
Any Mac or Powerbook made before 1999 will be lacking in many ways, no usb, no firewire, no airport, no ethernet on some, ram limitations, small hard drives,
I used to use and love Mac OS 6, 7, 8, and 9 back in the 90s, but they are so long in the tooth. OS 9 is so crash prone compared to X, not only that but there is almost no support even for OS9 apps anymore,
Aside from this I do understand why people love old macs, they are fun to set up and see what the OS looked like from as early as 1984.