That is the modulator; the replacement will have a plastic cap with a nipple, to use it cut the steel line about 4 inches from the end then connect a rubber vacuum line from the nipple to the end of the line.

Make sure you have manifold vacuum at the steel line, about 14’’ to 22’’ HG. If not the line is plugged at the engine side

The adjustment screw on the original modulator is behind the banjo nut.