I want 14.1 version

You can not update to iOS 14.

To update to the maximum of iOS 15.7.3, please see: Update your iPhone, iPad, or iPod touch - Apple Support

And: If your iPhone, iPad, or iPod touch won't update - Apple Support

If the above Apple articles do not help, please post back with relevant information. 

iOS 14 is actually not the latest version of iOS; it’s two years out of date. The latest version is iOS 16, and unfortunately, iOS 16 is not compatible with the iPhone 7/7 Plus. Here’s the list of iPhones that support iOS 16:

iOS 16 and iPadOS 16 are compatible with these devices - Apple Support

However, if you have the iPhone 7, I would suggest you consider upgrading to a new iPhone. You can check out all the latest models (or save on certified refurbished older models) on Apple’s iPhone website page. At this point the iPhone 7 is quite a bit out of date and missing some pretty key features. You’ll also notice faster performance and better reliability with the newer models.

Actually I should add that specifically, the latest iOS version is 16.3. But it’s only available on iPhone 8 and later. As the previous user stated, the latest security update for iPhone 7/7 Plus is iOS 15.7.3.