Find a stored procedure (or any text) inside a scheduled on on SQL Server 2008 and 2012 by querying the sysjobs and sysjobsteps system tables.
The following provides the name of the job and the step name. It uses the standard % wildcard so replace myjob in “%myjob%” below

SELECT name, "description", "enabled", database_name,step_name,step_id,command
       FROM "msdb"."dbo"."sysjobsteps" t1
              INNER JOIN "msdb"."dbo"."sysjobs" t2 on t1.job_id = t2.job_id
       where t1."command" LIKE '%myjob%'

More info on SQL system tables here:
MS Docs
MS Docs