I don't know that phone, but check your Contacts app's settings and see whether it has an option to export contacts to the SIM. Not all do these days - SIM storage is extremely limited, both in capacity and in what you can store, so most modern phones run exclusively off contacts stored in internal memory - but if it has the option that's where I'd look.
(I've not used SIM contacts for a decade now: when one of my SIMs died I never bothered copying anything back onto the replacement. Where I don't want to rely on some corporation's servers, or have contacts whose details I don't want to share with Google or similar, I can export to vcf as a backup that can be loaded into any contact management system, and hence is more flexible than a SIM card and without the limitations that brings).
