Are you wanting to do this in a query only or via code?
The starting point is likely
INSERT INTO tbl_JBPowerAssignment ("JbNo", "TermNo", "TB") VALUES (cboJbAdd, txtTermAdd, txtTbAdd)
It is the VALUES part that needs to be modified according to the answer. You threw in just about everything but the kitchen sink and the name of the form, so I'll make one up
If query, each has to be prefaced with Forms!frmFormName. and that form must be open and the controls must contain data to have any hope of getting anything meaningful out of it. Even if it's a query, there are other ways - a function comes to mind, but if you were going that route, might as well ditch the query and to it all in code.
Sorry, I skipped over most of the posted data example because it didn't seem relevant to my understanding of the problem.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.