I want to update my iPhone 6 I need ios 13 version

These are the iOS options based on iPhone Model --> You need to Identify your iPhone model - Apple Support

• iOS 15.1 —> 6S / 6S Plus, SE (1st Gen and 2nd Gen), 7 / 7 Plus, 8 / 8 Plus, X, XR, XS /XS Max, 11,11 Pro /11 Pro Max, iPhone 12, 12 Mini, 12 Pro, 12 Pro max, iPhone 13, 13 Mini, 13 Pro, 13 Pro Max
• iOS 12.5.5 —> Final release supported on iPhone 5S, iPhone 6/6 Plus, 

Learn how to--> Update your iPhone, iPad, or iPod touch - Apple Support

Unfortunately, the iPhone 6 is too outdated and it's hardware cannot support anything above iOS 12.5.x. iOS 13, 14 or the current iOS 15 requires atleast the iPhone 6s or 1st gen iPhone SE. Mind you, the iPhone 6 is from late 2014 and is therefore no longer supported.