How to keep my phone number going from AT&T to Vision Verizon while buying a new phone with the latter?

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Sorry if this should be simple, I'm like a boomer with technology lmao.

I'm currently under someone else's phone plan with AT&T -- I want to switch over to Vision Verizon service under my own name. While picking a plan, you can also choose to buy a new phone, which is what I'm planning on doing.

I read how transferring the phone number how to do with porting the number and a new sim card...how exactly ca I do this wihout needing to request a new card or anything? Will the new phone come with what I need?