Learn more about how use the Find My App
Find My - Official Apple Support
Then look at this Apple article and my additional advice below it:
https://support.apple.com/en-gb/HT201472
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
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 may never see the phone again.