You will need to get a birth certificate from the place where you were born. I do not think, you will get one from KTM, they will not usually issue one to you. However, you can get around in Nepal in things if you know people.

Best bet is to get from your own place. No translation is necessary if it is already in English. What are you talking about dude? Translate English in English. Make sure you have your dad's and mom's name, DOB and POB. Get it done in English. Ask for the letter pad before hand and get it printed in English from a computer institute or on your own and have them sign. It is easy. People in VDC and municipality usually helpful in doing this.

My above advice is based on my own experience - what I did and successfully went through, it is not based on FRIEND's or something.