Went to privacy and security on iPhone 11 and development mode is not there
Which iOS version do you run ? Must be iOS 16 or over.
Then, it is located at the very bottom of privacy and security page.
If not OK with iOS 16, have a look here: https://forums.developer.apple.com/forums/thread/716697
This may help as well: https://medium.com/@kshitijsharma94/how-to-enable-developer-mode-on-your-ios-device-and-find-your-udid-b3e46cea58a8#:~:text=Open%20Settings%3A%20Go%20to%20your,Tap%20it.