As per my understanding, you are trying to say that the manufacturers generally provide the B-H characteristics of the core , but the "hysterisis designer" tool of MATLAB plots the curve with "flux" vs "current". Therefore, you want to use the B-H curves provided by the manufacturer to program the "saturation characteristics" of transformer.
The term "H" in the "B-H" curves refer to the Ampere turns (product of number of turns "N" and current flowing in it, "I"). The "hysterisis designer" tool of MATLAB divides the Ampere-turns (H) by number of turns (N), which gives us the current (I). It is just link scaling the x-axis. The Hysterisis designer tool uses this "I" to program the saturation characteristics.
If you have the "B-H" characteristics of core from the manufacturer datasheet, first identify the number of turns (N) for your applications. After finding (N), divide the "H" values by "N". You will get the vector of currrents. You can use those current values to program the "Saturation characteristics of the "Three phase transformer" model in Simulink.
You can use the below formulla to find the number of turns (N) for your application:
where,
Generally, the manufacturer provides 
i.e maximum saturable flux density. But you can calculate 
from as:
i.e maximum saturable flux density. But you can calculate from as:
where, 
I hope this helps !
