I know I'm late to the party, but the model number will also tell you which is which. They've hidden it under the SIM card on the iPhone 8 and later models. From the Apple Support web site:
On an iPhone 8 or later, to find the model number, remove the SIM tray and look in the SIM tray slot. Make sure that you're in a place with bright light overhead. The model number is on the upper side—the side with the display.
Just for fun, here's the list of model numbers for all of the models up to now, August 2022, straight from the Apple web site.
iPhone 1st Gen:
A1203
iPhone 3G:
A1324, A1241
iPhone 3GS:
A1325, A1303
iPhone 4:
A1349, A1332
iPhone 4s:
A1431, A1387
iPhone 5:
A1428, A1429, A1442
iPhone 5c:
A1456, A1507, A1516, A1529, A1532
iPhone 5s:
A1453, A1457, A1518, A1528, A1530, A1533
iPhone 6 Plus:
A1522, A1524, A1593
iPhone 6:
A1549, A1586, A1589
iPhone 6s Plus:
A1634, A1687, A1699
iPhone 6s:
A1633, A1688, A1700
iPhone SE (1st generation):
A1723, A1662, A1724
iPhone 7 Plus:
A1661, A1784, A1785 (Japan)
iPhone 7:
A1660, A1778, A1779 (Japan)
iPhone 8 Plus:
A1864, A1897, A1898 (Japan)
iPhone 8:
A1863, A1905, A1906 (Japan)
iPhone X:
A1865, A1901, A1902 (Japan)
iPhone XR:
A1984, A2105, A2106 (Japan), A2107, A2108 (China mainland)
iPhone XS Max:
A1921, A2101, A2102 (Japan), A2103, A2104 (China mainland)
iPhone XS:
A1920, A2097, A2098 (Japan), A2099, A2100 (China mainland)
iPhone 11:
A2111 (Canada, United States), A2223 (China mainland, Hong Kong, Macao), A2221 (other countries and regions)
iPhone 11 Pro Max:
Model numbers: A2161 (Canada, United States), A2220 (China mainland, Hong Kong, Macao), A2218 (other countries and regions)
iPhone 11 Pro:
A2160 (Canada, United States), A2217 (China mainland, Hong Kong, Macao), A2215 (other countries and regions)
iPhone SE (2nd generation):
A2275 (Canada, United States), A2298 (China mainland), A2296 (other countries and regions)
iPhone 12 mini:
A2176 (United States), A2398 (Canada, Japan), A2400 (China mainland), A2399 (other countries and regions)
iPhone 12:
A2172 (United States), A2402 (Canada, Japan), A2404 (China Mainland, Hong Kong, Macao), A2403 (other countries and regions)
iPhone 12 Pro:
A2341 (United States), A2406 (Canada, Japan), A2408 (China mainland, Hong Kong, Macao), A2407 (other countries and regions)
iPhone 12 Pro Max:
A2342 (United States), A2410 (Canada, Japan), A2412 (China mainland, Hong Kong, Macao), A2411 (other countries and regions)
iPhone 13 mini:
A2481 (United States), A2626 (Canada, Japan, Mexico, Saudi Arabia), A2629 (mainland China), A2630 (Armenia, Belarus, Armenia, Belarus, Kazakhstan, Kyrgyzstan, Russia), A2628 (other countries and regions)
iPhone 13:
A2482 (United States), A2631 (Canada, Japan, Mexico, Saudi Arabia), A2634 (mainland China, Hong Kong, Macao), A2635 (Armenia, Belarus, Kazakhstan, Kyrgyzstan, Russia), A2633 (other countires and regions)
iPhone 13 Pro:
A2483 (United States), A2636 (Canada, Japan, Mexico, Saudi Arabia), A2639 (mainland China, Hong Kong, Macao), A2640 (Armenia, Belarus, Kazakhstan, Kyrgyzstan, Russia), A2638 (other countries and regions)
iPhone 13 Pro Max:
A2484 (United States), A2641 (Canada, Japan, Mexico, Saudi Arabia), A2644 (mainland China, Hong Kong, Macao), A2645 (Armenia, Belarus, Kazakhstan, Kyrgyzstan, Russia), A2643 (other countries and regions)
iPhone SE (3rd generation):
A2595 (United States, Canada, Puerto Rico, U.S. Virgin Islands, Guam, Mexico, Saudi Arabia), A2782 (Japan), A2784 (Russia, Armenia, Belarus, Kazakhstan, Kyrgyzstan), A2785 (China), A2783 (other countries and regions)