Can i use pg-40 cartridge in my printer

No, you can't. I have the same printer and tried to save a buck at Costco, where they sell a 41 and two 40's in bulk. However, the 40 wouldn't fit into the slot because the ridges are slightly different. Several online print websites list the 40 as being compatible, but it would fit on my iP6310D.
Take the 40 back and go somewhere that sells both the 41 and the 40.

Anyone who wants to buy 1 opened (but unused) and 1 unopened 40-ink cartridge, please email mjc_co@yahoo.com and I can either sell directly to you or put them on ebay. Thanks!