If you only want Apple OEM, you need this cable and the lightning to USB C adapter to use the 5W charger.
Lightning to USB Cable (1 m)
Lightning to USB Cable (1 m) lets you charge and sync your iPhone, iPad, or iPod to your Mac or Windows PC. Get fast, free shipping when you shop online.
store.apple.com
USB-C to Lightning Adapter
The USB-C to Lightning Adapter lets you connect your Lightning accessories to a USB-C-enabled iPhone or iPad. Buy now with fast, free shipping.
store.apple.com
I personally would just get a reputable aftermarket cable and not use the adapter, like this one.
Anker USB C Cable, [2-Pack, 6ft] Premium Nylon USB A to USB C Charger Cable for Samsung Galaxy S10 S10+, LG V30, Beats Fit Pro and Charging Cord for USB C Port Camera (USB 2.0, Black)
https://www.amazon.com/dp/B07DC5PPFV?ref_=cm_sw_r_apin_dp_FS0D17KME5JGD8DSNV1C