Choose the swap option here and when you activate the SIM it will be linked to your existing account, number, membership etc.
A replacement SIM does not cost anything.
You ask about numbers transferring which suggests that you are storing contacts on your current SIM rather than in the phone?
Contacts stored on your SIM will not be present on a replacement SIM so you'll need to find a way to backup/restore/copy these to your new phone.
Hope this helps.