Looking for Conrad from Northumberland County Pennsylvania

My mother's maternal side of the family was CONRAD and they settled in Northumberland county Pennsylvania sometime during the 1700s. Peter Conrad came from Germany in 17?? to Northumberland county Pennsylvania and is buried there. The rest of the family moved to northern Indiana in 1837 or 1838 near Elkhart Indiana at Millersburg.
In 1877 te family moved from Elkhart county Indiana to Billings, Missouri and bought a farm north of Billings one mile north.

I am having trouble finding the year that Peter Conrad came from Germany and if anyone came with him. I do not have a name for the wife of Peter CONRAD or how many cildren he had but I think there were four sons and one was Jacob CONRAD.

I am also trying to locate the Solomons Creek graveyard near Benton, Elkhart co. Indiana, Jacob CONRAD was buried there -- year of death unkown.

These are the brick walls that I have come up against in my search.