Mmy unfiled return has reported the cost basis for stock bought in 2006, but I inherited the stock owned solely by her when she pasted away in 2010.

If it was solely your wife's stock, and you inherited it, your basis would be the value on the date of her passing. 

NOTE- If the stock was purchased with community funds while you lived in a community property state, you would only step-up half the basis. 

If the stock was her property exclusively, then you step-up the full value to the 2010 value.