So can i buy a sata to 6 pin adapter or i must buy a new PSU?
Never use any Molex to 6-pin or Sata to 6-pin adapters.
The graphics card i got it says at the description that i need at least 600 W PSU tho
GPU makers tend to overstate the need, because they don't know if you're running a modest system, or a high-end system overclocked like crazy, etc, so they need to hedge their bets.
So, it's not necessarily about the total wattage numbers, but about how good of a quality the PSU is. Also note, Bronze, Silver, Gold, etc., rating is an efficiency rating, but says nothing about the quality of the PSU's innards.
Click on the first link in my signature - that should be your guide to selecting a quality PSU. The PSU is...