I've bought a Sapphire PURE White E350 (IPC-E350M1W) Mainboard probably the wrong RAM: Corsair Memory — 4GB DDR3 SODIMM Memory (CMSO4GX3M1A1333C9)
Can I use the SODIMM RAM with this mainboard or do I have to send it back?
No, that's laptop RAM (204-pin) vs. Desktop RAM (240-pin). You have the lappy RAM, which does you no good on a board for desktop. Be sure you get 240-pin DDR3.
It won't even fit in the slots. So send it back.