Please how can I update my iPhone 6 in safari net here because am unable to update it in the settings on my phone

You cannot update your iPhone in the Safari app. You can update your iPhone wirelessly in Software Update menu, or via a computer. You should be aware that the iPhone 6 cannot be updated further than iOS 12.5.7

You can check your current version here:

Settings → General → About

You can download and install software updates here:

Settings → General → Software Update

Remember to connect to Wi-Fi and a charger. Your iPhone must have more than 50% power to update without a charger connected.

You can find more useful information here:

Update your iPhone or iPad - Apple Support

If your iPhone or iPad won't update – Apple Support (UK)

If you want to update your iPhone via a PC or Mac, see here:

• Mac: Update your iPhone, iPad, or iPod touch with the Finder - Apple Support
• PC (iTunes): Update your iPhone, iPad, or iPod touch with iTunes - Apple Support