New phone SIM card

[Longbarn5]

I am getting a new phone for my daughter. Currently she has an old I phone but very unusually doesnt really like it so the new phone will be a different type. She will want to keep the same number so how will I know if the SIM in her iPhone will fit it?

What model is she moving from and to? The apple site should say whether they use nano or micro etc sims

I have actually just found that you can get a kit to basically change SIM sizes so all good I think. Thank you though. Good point