Hi imahumble1,
To clarify, the USB-C cable is only to charge your Beats Flex earphones. They connect to your iPhone, iPad and Apple Watch using the Bluetooth connection, not a wire.
For charging, this adapter will work. Buy 20W USB-C Power Adapter - Apple
If you don't want to purchase a new adapter, you can get a USB-A Cable with USB-C Connector cable, like this: mophie USB-A Cable with USB-C Connector (1 m)
The steps below will help you pair to your iOS devices.
"Pair your Beats Flex - Learn how to pair your earphones with your device.
Pair with iPhone, iPad, or iPod touch
- Make sure that you turned on Bluetooth on your iPhone, iPad, or iPod touch.
- Hold your earphones next to your unlocked iOS device.
- Press and hold the power button on your earphones. When the indicator light flashes, your earphones are discoverable.
- Follow the instructions that appear on your iOS device.
If you can't connect to your device, learn what to do."
You can find this information and helpful details here: Set up and use your Beats Flex earphones
Hopefully that helps clarify the difference between charging your Beats Flex and connecting them to your devices.
Best!