So i bought a series 6 Apple Watch and it has the cellular ability. It came with a new number and i didn’t know about it until i looked at the receipt. Do i need the new number for the Apple Watch or could i just use it as the same number as my current phone?
The watch actually uses the phone's number. You don't need to do anything with that number.
M1 Mac mini, macOS 11.3; Watch, series 5 GPS/cellular, watchOS 7.4; iPad Pro 2nd Gen, iPadOS 14.5; iPad Air 2, iPadOS 14.5; iPhone 12 Pro, iOS 14.5; TV 4th Gen, tvOS 14.5 HomePods, audioOS 14.5 and Airport Express w/ Airplay 2