Everything flows naturally from its higher concentration to lower concentration. Same concept works here also. When two oppositely charged conductors connected through a wire, the conductor having positive charge is of higher potential and the conductor having negative charge is of lower potential.

But, if we talk about the concentration of negative charges, its higher on the negatively charged conductor.

So, the negative charges flow from lower potential (Higher concentration of negative charge) to higher potential (lower potential of negative charge).

If we talk about force, so the negative charges on negatively charged conductor experiences the force of attraction towards the positively charged conductor, and so, they flow from lower potential to higher potential.