I just bought my Phantom 3 SE. But, I can't connect the cable to my Samsung S9. One end of the cable connects to a small USB port on the controller but the other end is a full size USB plug. The S9 has a small non-standard USB port. Does anyone know where I can get a cable to connect the controller to my phone? Specifically, what cable do I need?
Thanks in advance.

Look at a USB-C cable.

In my S9 box there was a conversion plug from usb-C to usb-mini included. If you also got this plug, then you can try that.

Edit:
Sorry, the above is for the direction way. But again in my S9 box there were two converter plugs included, so the other one should work.

A P3SE uses WIFI to transmit any signal from the bird via RC to the phone and it´s bidirectional. Put yur phones WWIFI on and log in to your Phantoms WIFI SSID. Thats all.

Hi there, thank you for reaching out and sorry for the trouble. With regards to that. You don't need to connect a USB cable from the Remote to the Device. Since the connection between the remote controller is through WIFI. You just need to search or scan the WIFI of the remote from your device and the password is 12341234. Best regards!