This should not be hard either if your vacuum pump is powerful enough for the cow milker. Here is how: get a cow cluster with hoses (milk and double pulsation hoses). Replace the goat cluster with the cow set from the bucket and pulsator. Please note, goat cluster has only a single pulsation line, while most cow milkers have a double pulsation line, or some may have 4 pulsation lines to the pulsator. Usually, goat milker use only one outlet of the 2 (or 4, depends on the model of the pulsator) and the other(s) get blocked. You need to use the blocked outlet at the pulsator too for cow cluster connection.
Pulsation rate: Please note, goat milker may need a fatoer pulsation (100 p/m) while most cow milkers are set at 60 p/m. You may need to change the pulsation rate or get another pulsator that is set for goat milking. Follow manufacturer's direction on to make such adjustment.