How to create the field mapping in Azure cognitive search

I have been using the Azure cognitive search to create the search index where the data source will be the azure SQL database.

I have created the search index for azure cognitive search and for the key index will be the id column from the table and the datatype will be fixed as edm.string type.

I have seen that we can change the datatype of id column to edm.int32 using the field mapping.

Can anyone help me with how we can able to create the field mapping for id column by changing the datatype to edm.int32