you've got to match the voltage of your controller. It should say the voltage inside on the PCB, or If not the capacitors on the board will have a maximum voltage. 35v is probably a 24 v controller, 50 v capacitors is probably 36 v controller, 63 volt capacitors minimum for a 48 v controller. Capacitors look like little oil tanks with a minus stripe on one side of the plastic wrap.
For $189 I got a whole DD hub motor in wheel, controller, throttle, brake handles with switches, connector blocks. I wouldn't spend more than that, just throw away the stuff on the bike already. Batteries are not cheap, I got two duds for $320 from ebay & amazon, use Luna, ebikeling, or maybe californiaebike among US banked suppliers. Sending your debit card # to asia is IMHO, risky.