If you move your sim card to an Iphone will it keep your contacts?
It depends if the original phone the SIM card belonged to was
saving them to the SIM card itself. Here's some clarification:
The SIM card will retain contacts from a previous phone.
The iPhone will not recognize SIM contacts until they are
imported to the Contact list via Settings > Mail, Contacts,
Calendars > Import SIM Contacts
The iPhone does not save contacts to the SIM card, and therefore
if the SIM is from an old iPhone there won't be any SIM contacts
present.