where I could request a list of jobs that used a certain part number
If tblParts is akin to inventory, it doesn't belong with tblJobs. Inventory is one entity, jobs are another. To query like this would require tblJobParts where JobID 456 shows up 10x if it requires 10 parts. You would index these fields as a pair so that the same JobId and part number cannot appear more than once - provided you are not trying to break out parts on a per task basis (e.g. qty 10 of 5874 required for one phase, but 20 more for another phase. In that case, the parts become related to the task, not the job. You can relate the PartID to the inventory table to see if the quantity in stock is sufficient, as well as query "backwards" through tblJobParts for a list of jobs related to a part id.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.