Converting string field to integer

I am getting the value of a field name "fcs" through pattern but i want this to be in integer format, but when i open settings in kibana, it says this field has string type. Can anyone tell how to resolve this issue ?

Pattern =>
%{DATA}fcs-errors-stat%{DATA}%{SPACE}uint64_value: %{NUMBER:fcs:int}

my input =>
fields {
name: "fcs-errors-stat"
fields {
name: "data"
uint64_value: 0

Check the mapping of the field in ES, you may either need to use a mutate + convert to be sure, or map the field in ES with a template.

Thanks, I actually need to create another new index. It couldn't update type for previous indexes.