How to see what I'm doing on my nikon d3100 LCD monitor on my computer?

Is there a way i can see what I'm currently shooting on my d3100 on my computer?

The term you are looking for here is "tethered shooting".

All my Canon cameras came with the necessary software to do that, as well as the cable. Other brands, such as Nikon, can do it, too, but you need to purchase stuff for it.

Now that you know the correct term, you'll be able to simply Google for more help - there are tons of tutorials available to help you learn how to set it up (for example: https://www.google.com.au/...9&bav=on.2, or.r_gc.r_pw.r_cp.r_qf., cf.osb&biw=1920&bih=995 )

It's called tethering, and it's almost never supported in entry level dSLRs like the D3100.It's almost always supported in semi pro and pro dSLR bodies.