HJ makes 3 jacks with different load ratings and the load in amps from the motor will vary depending on the weight it is lifting. You could contact the manufacturer. They might be able to ballpark if you can give them the weight although I think they may just give you the max rated amperage of the motor/controller/fuse.
Typically the fronts are working harder than the rears due to weight being higher on most slide in campers.. The rating of the fuse would tell you what they consider a max amperage to protect the wire. If the camper is 1200 pounds the jacks will draw much less amperage than if i's 6,000 pounds. Rears will be less than fronts.
For best results in reducing the amperage a motor needs make sure that the jack controller is located near a strong battery and cabled properly to avoid voltage line drop which will increase current to the jack motor. This can really come into play if you are raising all the jacks at the same time without enough battery to keep the voltage from dropping.
So, lots a variables to your question.
Other than that you could invest in a cheap clamp on dc meter that would tell you exactly the amperage at each jack. This is the one I carry to satisfy electrical questions that I have. I haven't tested this on our camper. Next time I'm loading it I'll see what the amperage is for curiosity.
clamp meter