how can I change image size by with image URL

can anyone tell me what to append to an image url to control it’s size?
I have data feeds where the size of the image urls is not consistent.
example
http://images.doba.com/products/4030/nmcpics_021_021214PR_IT_IM.jpg
which is 1200px 1200px
somewhere I have seen similar URL’s with some code at the end to reduce the size like
http://images.doba.com/products/4030/nmcpics_021_021214PR_IT_IM.jpg?size= “w350” “h350”
Now I know what I added is wrong, can anyone tell me the correct syntax?
michael