So, to get the benefitGeneralID from the response, we simply loop through the data, test for the required condition and save the required value,
One way to do this is:
//Saving the response from the GET request
var response=pm.response.json();
//Fetching the data array and storing it
var data=response.data, Ids=[]; //Ids to store benefitGeneralID
//looping through each data item
_.each(data, (item)=>{
//Required condition
if(item.uniqueCode==="name123code")
Ids.push(item.benefitGeneralId);
})
console.log(Ids);
Good luck!