Want to put some blocking in wall don't know what height

Typically you want an 18" back splash. Assuming 36" from floor to counter top, that means the bottom edge of the cabinets would be 54" off the finished floor. Of course depending on the layout of your cabinets some may be higher (or lower) for specialty items such as wine racks, microwave, hood, etc.

This will depend on whether it is a floor or wall cabinet. The cabinets should have a strip at the back top for hanging or affixing the cabinets. EB has given you the standard industry norm for a cabinet install. You can set a floor cabinet on the wall and then see where the hanging strip in placed. Lots of builders install 2X6 or 2X8 in the wall with the midpoint at 35" so you have some adjustment room. Measure up 18" from the finished top and that is where a standard wall cabinet bottom is set. The top hanging rail depends on the cabinet height but use the same format as for a base cabinet. Good Luck