How do I update this iOS?

the phone shouldn't need updating to use a SIM card, what issues are you having, please describe in detail.

If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad - Apple Support

Update your iPhone, iPad, or iPod touch

• If you have an iPhone 5S or 6/6plus, the highest you can update to is 12.5.7

• If you have an iPhone 6S through 7, or SE 1st generation, you can update to 15.7.6

• If you have an iPhone 8 or higher, or SE 2nd or 3rd generation,you can update to 16.5

Go to Settings > General > Software Update.

This link will show you how to update your iPhone, iPad, or iPod touch using WiFi -

Update your iPhone or iPad - Apple Support

This link will show you how to update using your computer -

Update iOS on iPhone - Apple Support

othman106 Said:

"How do I update this iOS?: I need to update this phone to use a SIM card"

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Provide a Screenshot of this Message::

Can you provide a screenshot? that would most certain help. Go here: Take a Ccreenshot on your iPhone - Apple Support