On your new iPhone, go to Settings > Cellular, tap Set Up Cellular or Add eSIM, then tap Transfer From Nearby iPhone or choose a phone number. On your previous iPhone, follow the instructions to confirm the transfer. Note: After your phone number is transferred to your new iPhone, it stops working on your previous iPhone. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.