This WLToys XK250 comes with a mode I transmitter, which means thrust control is on the right hand side. There is nothing you can do to change this. You can, however, consider to use an OpenTX transmitter to replace the stock one.
Mode 1 and Mode 2 are the two most common transmitter stick configurations used in RC planes, helicopters, and drones. They define how the control inputs for throttle, elevator, rudder, and ailerons are assigned to the transmitter’s sticks. The choice between Mode 1 and Mode 2 largely depends on personal preference and regional popularity.
Mode 1 is often preferred by pilots who want throttle and aileron controls on the same stick, which can be helpful for aerobatic flying. In contrast, Mode 2 is more intuitive for many beginners and better reflects the control layout of real-world aircraft, making it the standard choice in many countries.
I personally prefer mode II where thrust is on the left.