Be best to clean the trash out of it, It may be that simple. Rotating the motor backwards may help.
If you do not know the model then parts will be hard to find. You will need new seals, at minimum, if you take it apart.
Trash in the impeller can lock one up. Maybe could be the start switch, or a cap if it uses one.
Watch out for electrical Shock. Kill the power Power first. (You asked, be safe)