how do you mean? Using teraterm you should come directly to a login prompt once boot is finished and after entering the credentials you should see a Linux console. "ls", "cd", ... are supported (unless you changed the busybox configuration in a weird way)
So not quite clear what you ask for
presently, I want to access the directories/files/sub-folders on SD card(which has already booted up).
Which is the better terminal that I can use for it and much more in detail that which commands should be passed. ?Kindly help
Why not sticking to TeraTerm which you already have installed? (alternatively PuTTy, ...)
if you can see the machine booting in TeraTerm I suspect you're connected to serial. So everything should be fine. Don't get your issue