Two answers, depending on which screws are out
Now, on the stand off there is a screw that goes through the ladder into the standoff.. The nut inside the standoff is captive, you simply replace the bolt (it's a bolt not a screw even if it has a screw head)
If it's the bolt on the other end Remove the screw from the ladder, remove the bracket from the RV, replace the bolt (you may have to do some work here) and then remount the stand off and then replace the bolt in the ladder.,
Again the nut is captive, it did not go anywhere.,