SIM card questions as I prepare to change to a new cell phone carrier

Do I need to worry about personal information on my iPhone's SIM card when I change service carrier? Does my iPhone's SIM card carry my phone's personal information such as contacts, pictures, videos, apps, notes? If yes, how do I clear it without having to clear my phone?

I was told by the new carrier (Spectrum) that I will need to change SIM cards when I get their service. When that happens, do they keep my old SIM card, or, is it given to me to destroy?

Thanks.