The quickest way to verify your iPhone model is to locate it in your phone’s settings menu.
Go to Settings > General > About > Model Name
You can also identify your model number and cross reference that number on Apple’s website.
Go to Settings > General > About. To the right of Model Number, you'll find the part number. To find the model number, tap the part number.
Next, check your model number on Apple's site.
If your iPhone does not power on and has a SIM tray, you can locate the model number removing the SIM tray and looking in the slot. The model number is on the upper side near the display.
iPhone models that support only eSIM don't have a SIM tray. To find the model number for models without a SIM tray, look in the Lightning or USB-C connector. You'll find the model number on the upper side of the connector.
More information on finding your model name and number.