Transistor / mosfet for PWM dimming of 30W RGB LED
Well, the specifications of the device you linked are grossly inadequate.... but given you have 10 LEDs in series, I expect you'll operate at something like 40VDC...

Arduino analogWrite function generates PWM at about 490Hz.

I would suggest setting up a high side switch with a P-channel MOSFET (e.g. IRF9Z24) conrolled by an NPN BJT (e.g. 2N3904). Say 100ohm resistor into the base of the BJT and a 4.7kohm pullup on the gate of the MOSFET. Connect LED between MOSFET drain and GND. Connect PWM input to the aforementioned 100 ohm resistor.