Change the datatype of the field in a table in Bigquery?

In a Bigquery table, I am having data. I want to change/upgrade the datatype of one the fields in the table.

Current Table structure: Name:String , FlatNumber:Integer,Address:String, Amount:Integer

Required Updated Table Structure: Name:String , FlatNumber:String, Address:String, Amount:Float

Note: I am having data in the table