Hi Priya,
You can use concatenate to join field values.
Syntax of CONCATENATE(str2,str2)
For your question, you can use multiple concatenate() using delimiter in between to combine them.
concat = CONCATENATE([id],CONCATENATE("-",CONCATENATE([Mon],CONCATENATE("-",CONCATENATE([year],CONCATENATE("-",[Locn])))))).
Hope it helps you.