What's not in the iPhone SE box?

Hello,

Use a charging adapter and cable from a previous iPhone, or use the cable that came with it and get this:

20W USB-C Power Adapter - iPhone Accessories 

The USB-C combination will give you the added benefits of fast-charging:

Fast charge your iPhone

Good luck.

If you purchased this 2020 (2nd generation) iPhone SE directly from Apple, it should include a USB-C to Lightning cable ... but not a power adapter. MrBill3 has already identified a proper adapter for you.