how to find my iphone turn off find my?

You cannot if Find My was turned off on the phone.

If it was turned on, find another device and in a browser sign into

https://icloud.com/find

anf if you type it in like that you will not need 2FA codes

stolen or lost

Please  look at this Apple article and my additional advice below it:

If your iPhone, iPad or iPod touch is lost or stolen – Apple Support (UK)

Tracking lost or stolen phones

The 'Find My' tracking is to help you discover if you left your phone in the office or the restaurant. Lost or Stolen phones are rarely ever seen again.

Risk mitigation

Get your provider to 

Cancel your SIM.

Send you a replacement SIM on same number.

You can then put the SIM in another iPhone to get the codes you will need.

Phishing warning

Its possible for a thief to obtain your phone number particularly if you did not have a PIN set on the SIM.  So do not respond to texts to sign into your account! They are NOT from Apple!

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support (IN)

Resign to the fact that if you had a passcode set and you do not provide your Apple ID via phishing texts then your data is safe but you will never see the phone again.

Find My

Learn more about how use the Find My App\

Find My - Official Apple Support

See the following from If Find My iPhone or Find My iPad isn't enabled on your missing device - Apple Support

If your missing device doesn't appear in the Find My app or at iCloud.com/find, you didn't turn on Find My. There's no other Apple service that can find, track, or flag your device for you. But there are steps that you can take to help protect your data.

That article has other information that you may want to read.