I want to know position of dimmer switch in power supply to standard lamp with halogen lamps and an in line transformer. Is it between power plug and transformer or transformer & lamps

"standard lamp with halogen lamps"

Means what?

"standard lamp" is a table lamp?
Understand that "lamp" to an electrician means the part of a light fixture that emits light, the bulb, the fluorescent tube etc.

Do you have a low voltage fixture powered by a transformer that uses household line voltage?

First thing we want to to know is whether this is made to be used with a dimmer, some things are not dimmable unless they specifically say they are dimmable.