Hi Julia and welcome to the forum…
Are you saying you have a cigarette type plug that converts 12v to 5.1 and it doesn’t work?
When you say it isn’t working can you provide details?
- Does the led light come on on the phone?
- Does it say charging slowly?
- Are you able to charge the phone otherwise?
Here is a page by Belkin
Assuming you have a suitable usbA to usbC cable
Here is a simple single adapter that should provide a quick charge