Compatibility summary
You will need a travel adapter in Montserrat; plug types used there differ from Switzerland.
Plug comparison
Switzerland plug types: C J
Montserrat plug types: A B G
There is no common plug type between Switzerland (C J) and Montserrat (A B G). You need a travel adapter.
Voltage comparison
Switzerland: 230V, 50Hz
Montserrat: 230V, 60Hz
Voltage difference is within a range many devices tolerate; check your appliance label.