To design a transformer, pure mathematical calculations are actually quite difficult. It is recommended that you first look for the ferrite skeleton, which generally does not need to be too big, and then come back and wrap it yourself. The primary one usually has 5-20 turns, and the secondary one usually has 180 turns. Try more, and you can usually find it within 7-10 times. If you are quite satisfied with the winding scheme, then take the sample to the transformer manufacturer to trial-produce the sample.
It should be noted that if your ultrasonic product needs to be used stably in an environment below minus 25 degrees, this will involve a military frame. Just find a military power supply manufacturer to design it. Of course, the cost of the transformer This will increase 10-100 times.