How can I locate my iPhone if it’s off line ?

The phone must be turned on and connected to the internet in order to send a location signal. See this link...

If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

Several things have to be all working together for the Find My feature to work correctly:

1. Find My must have been enabled on the iPhone
2. The iPhone needs to be powered on
3. The iPhone needs to have an Internet connection

If one of the these things is missing, then you won't be able to see the iPhone on a map.

Since you note that Find My is "off" in your post above, I'm afraid that the first condition above cannot be met. Hopefully, you will enable the Find My feature on your replacement phone. Once enabled, I can't think of any reason why you would want to disable it.