You can either move to the same type of phone, such as Android to Android, or move to a different type of phone, such as iPhone to Android.
If you’re moving to a different type of phone:
Download WhatsApp on your new phone and register your phone number.
If you forgot to delete your account associated with your old phone number and don’t have access to your old phone, all of your account information tied to that phone number will be deleted if the new owner of your old phone number activates WhatsApp on a new phone after 45 days.
Note: If you give away or return your old phone to your mobile provider, make sure to wipe it of all your data beforehand, including the SD card if applicable. This ensures none of your private data, such as your WhatsApp chat history, will fall into someone else's hands.