This is a good question. Because you might reach a wrong interpreatation if you was not careful when chose unit for the ststem. $\vec{F}=q \vec{v}\times \vec{B}$ is used to calculate the motion in the simulation.
For a simulation, the same length in the simulation can be 1cm or 1m or 1km.
It depends on how you interprete the system.

In the above system, you can select the unit of B as Tesla, then the unit in space (x,y coordinate) will be meter, charge will be Coulomb. Unit for velocity will be m/s.

If you want to interprete it as a real electron:
q[sub]e[/sub]=1.6 10[sup]-19[/sup] C, m[sub]e[/sub]=9.1 10[sup]-31[/sup]kg.
m_e/q_e=5.69 10[sup]-12[/sup] kg/C,

If you want to interprete B as Tesla,  then the unit of 1 second in the simulation represent 5.69 10[sup]-12[/sup]s in real case. It means that the electron will move very fast. However, it can not be faster then speed of light c=3 10[sup]8[/sup]m/s (less than 0.01c will be fine to ignore relativistic effect), so the unit of length can not be meter(m). However, $\mu$m (10[sup]-6[/sup]m) can be used.

If the unit of B is selected as gauss (1 gauss=10-4 Tesla), then unit of length can be selected as mm (10[sup]-3[/sup]m).