Change Character value of timestamp to Timestamp value

Hello Grafana Community!
I am trying to get the difference between these two time columns to get a an over all lag time. using this query and cannot get my timestamp which is in a character value to display in a timestamp with zone value. I keep getting the error

  1. macro __timeGroup needs time column and interval and optional fill value
    2 .pq: date/time field value out of range: “20200306152924266976”

     ```
     SELECT
     $__timeGroup(timestamp(sv_timestamp),$__interval,900000),
       count(dbms)  - count(sv_timestamp) AS "Time taken"
     FROM share."APPLE"
     WHERE
       $__timeFilter(timestamp(sv_timestamp))
     GROUP BY 1
     ORDER BY 1
     ```
    

I believe its because its a character value but I am not sure