Do you have a ruler? If so you can measure the dimensions of the envelope.
Then in Word 2007's Print Envelope section you can find the closest match in size then use the options there to move the address around until it places where you want it.
Printing envelopes is never easy and you will often waste one or two before getting it right. What I do, is to type my address on a blank document and position it where I think it will print, then insert either an A4 or A5 sheet of paper into the printer and try printing using the print envelope options until I get it about right.
I have got an envelope. But i don't know its size. Is there any software that I can use to print envelopes. I tried all the sizes of Office 2007 but its not perfect.