Gene is correct. Most times, for things like rooting software, it's not installed and its location is not added to the system PATH variable. You need to be sitting in the folder/directory where that software is located, or you must fully qualify the path to the exe file.
It's usually much, much easier to change directory (and the command is CD) to the location where the thing you're trying to run is resident. If you don't and its folder is not part of system path, you will get precisely the error message mentioned at the outset.
Brian - Windows 10 Pro, 64-Bit, Version 20H2, Build 19042
Always remember others may hate you but those who hate you don't win unless you hate them. And then you destroy yourself.
~ Richard M. Nixon