Checked a few websites. From my place, can take MRT to Kranji station, then change to Causeway Link bus. Causeway Link bus goes to Larkin. Have you been to Larkin before? Is it a good shopping town or just an isolated terminal?
As Spiky as pointed out Larkin is a bus station. It's better to go to that bus stop between the CIQ building & new KMT coplex or at JB Central , next to City Square Mall & catch a bus to one of the malls. Some malls were offering free shuttles on weekends, I think it was Terbau?? Don't know if they still do that.
Cab fares in JB are reasonable. Could just target a few malls & take a taxi there.