im getting a 1 gb hd 6670 (r6670-md1gd5) from msi and my psu doesnt have connector cables for a gpu will the gpu need to be plugged into the psu
That particular card does not require one, but higher end cards do.
If your PSU doesnt have built in 6/8-pin connectors higher end cards generally come with the required 4 to 6 molex cables, or you can buy them and they are quite cheap.
Any GPU that needs 75W or less will only need the PCI-E power while higher end cards like a 550 or really any gaming card will need a 6 2x6 pin 6 and 8 or 2x8 pin power.