When you log into an account with Steam Guard it should ask you for the code in the same window. Its possible this is now broken due to Steam having changed the way logins work a while ago. Can you try running npm update and then node index.js and see if that solves the issue for now?

Upon running the npm update I received
"added 17 packages, removed 199 packages, changed 16 packages, and audited 90 packages in 4s"
After running "node index.js" I was met with:
"Error: InvalidPassword
at Steamuser._handleLogOnResponse (C:\Users\123|Desktop\fake-stattrak-master\node_modules\steam-user\componets\0-9logon.js:775:17)
at C:\Users\123\Desktop\fake-stattrak-master\node_modules\steam-user\componets\o9-logon.js:400:10 {
eresult: 5
}

I did not receive any prompt to enter a steam code.

In my test it appears that I can login fine after upgrading all dependencies but my strange weapon doesn't appear to gain any kills. Not sure why and I am not really gonna bother looking into it.

That's fine, thanks for responding at all :)