how do i upgrade from iso 9.3 to iso 10.0

WhatsApp will no longer be available on the iPhone 4 and 4S from November 1, 2021, WhatsApp for iPhone requires iOS 10 or newer and has been discontinued as of November 1, 2021 with support for Apple iPhone 4 & 4S

It is not possible.

iOS 9.3.6 is the latest iOS version for iPhone 4S, can’t be update to a higher iOS.

whathsapp iphone 4