how do i reconnect my apple watch to my iphone 11 from my iphone 7

This link will help you --> How to pair your Apple Watch with a new iPhone - Apple Support

Your Watch can only be paired with one iPhone at a time, so if you're upgrading your iPhone from a 7 to 11, you can either install your iPhone 7's backup onto your iPhone 11 to preserve your Watch's settings, or erase your Watch and set it up fresh with your iPhone 11.