How to find a i3 processor is 1st generation or 2nd generation

If its an i3-XXX , its first gen (Nehalem or Westmere). You can also tell because its on a different socket to the others (LGA1156).
If its an i3-2XXX, its 2nd gen (Sandy Bridge).
If its an i3-3XXX, its 3rd gen (Ivy Bridge).

Some one correct me if im wrong but that i think would be like an 1156 socket for very first if not it was 1155 but think they made a few for the 1156 and just search for that socket 1156 or 1155 which ever u want. They definatly made them for the 1155 and still do thats the current socket..

simply check this
nehalem is 1st gen
sandy Bridge is 2gen
ivy Bridge is 3d

First generation i3s (and i5s and some i7s) only used socket 1156, and had three digits to show its name (like all first generation Core i3, i5, and i7s).

Second generation AND third generation i3s (and i5s and most i7s) only use socket 1155, and have four digits to show its name. However, second generation is easy to tell apart from third generation due to naming schemes. As manofchalk said it, i3-2XXX is second generation, whereas i3-3XXX is third.

No 1st gen CPUs will work on socket 1155 boards, and no second or third generation will work on socket 1156 boards.

Or you can simply download a program called CPU-z which will identify your CPU model, motherboard, RAM, and graphics card.