What is the relationship of distance from magnet and strength of the magnetic force?

This depends upon the size of the magnets involved. If it’s two longish bar magnets, then the force decreases as the square of the distance. E.g. double the distance means force is 1/4. So this applies as long as distances between magnets are small compared with the magnets’ lengths.
This is because the force law between isolated poles is the same as that between two gravitating bodies, or two isolated electric charges