I tried to lock my phone and this pops up

7T22 wrote:

well yes it does has a USBC cable but it won’t fit in my phone I only use it to charge my iPad

That makes no sense.

Presumably you’re talking about an iPhone 12 Pro. It comes with a USB-C to Lightning Cable, which is also presumably what you’re talking about. Naturally, the Lightning portion of that cable fits in your iPhone.

Means you need to restore your device.

If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

You are viewing the restore screen.

If you see the Restore screen on your iPhone, iPad, or iPod touch - Apple Support

Use the USB-C if (and only if) your computer has a USB-C port. Otherwise, use a USB cable.

7T22 wrote:

But why?

To answer that, we would need a complete scenario of all your iPhone’s activities.

Glad that answered your question. Enjoy your iPhone.