The -g prefix in cmd does not work, what to do?

Question

Node.js

Faced the following problem
Error code:

C:\Users\Admin>npm install -g npm
"CALL "C:\Program Files\nodejs\\node.exe" "C:\Program Files\nodejs\\node_modules\npm\bin\npm-cli.js" prefix -g" не является внутренней или внешней
командой, исполняемой программой или пакетным файлом.

In addition, when calling, for example, the command npm -version, the same message:

Everything was fine before, there are suspicions that a similar failure could occur after trying to install the wget program (for downloading sites), which I tried to install, but it did not work, so I poked around in "Environment Variables / Path", then it didn't work, deleted it ..
at first I thought that the problem was here, so I reinstalled it 1 time in the usual way, 2 times additionally deleted the npm folders from the "Roaming" folder, rebooted the computer, in general, like "did all he could."
Add. screenshots:

I hope that the problem will be solved by correct setting of variables in the system properties.
Could you see the contents of Path on your computer? Well, I'm like that .. you never know.
PS: in which directory are packages installed with the -g option?