whatever it is , it will not be spelt like that. At a guess, it may read "MynyddyGarreg" ( What looks like an "o" maybe an A and your "W" maybe R's, and the Y could be a G) , which is a place near Kidwelly I believe, which in turn falls into carmarthen.
The first part of your word is probably Mynydd y something. ( N's look like U's in many writing styles in those days. I don't know why they wrote the N's like that back then, but nearly everything I have and seen the N's tend to be written like the way U's are written today)
Maybe you could post up the image of the address part, and see if anyone can work out what it says. But Myuydd is all wrong in Welsh, it will most probably read Mynydd -y -"something"
The place called " Mynydd - y -Garreg" ("Mynyddygarreg), kidwelly area is my best guess ( but it could be Mynydd y "anything") at what it may actually read without seeing the writing
Hope that is of some help