What is the force in terms of Coulomb's constant between two electrical charges of -1 C and -2 C that are 4 m apart?

Use that describes force between static electrically charged particles. In its scalar form the law is:
##F=k_e|q_1q_2|/ r^2##
##F=8.9910^9 Nm^2 C^-2|(-1C)(-2C)|/( 4^2 m^2) = 1.1210^9N##
That is a large force it should give you an idea how large a coulomb really is. It’s a huge amount of charge
Use Coulomb’s law that describes force between static electrically charged particles. In its scalar form the law is:
##F=k_e|q_1q_2|/ r^2## where ##k_e = 8.9910^9 Nm^2 C^-2 ##
Now substituting the given charges and distance of separation:
##F=8.9910^9 Nm^2 C^-2|(-1C)(-2C)|/( 4^2 m^2) = 1.1210^9N##
That is a large force it should give you an idea how large a coulomb really is. It’s a huge amount of charge