can we get the SLI for this onboard HD 3200 and Nvidia GT240?
Oh, it hurts....
The AMD 780G chipset uses an integrated AMD/ATi Radeon HD 3200 GPU.
AMD/ATi's vendor specific multi-gpu technology is Crossfire (CF); SLI is Nvidia's multi-gpu tech. They are in no way, shape or form cross compatible.
While it is entirely possible to have an Nvidia card in a motherboard with an AMD/ATi integrated gpu, you will never reap multi-gpu rendering benefits from such a setup.