Unable to map from job to to job in manage job mappings

We have a custom report to calculate direct, overhead, g&a, profit. For this calculation I need to derive from job name from the to job name of project invoice lines. Unable to map from job to to job in manage job mappings page. Need some information on the same where it's maintain from back end. I checked below tables but I am unable to link the from to to job.

select * from PJF_RATE_SCHEDULES_VL
select * from PJF_RATE_SCHEDULE_LINES
select * from PER_JOBS_F_TL