I have Pi3, I have Raspbian image, I need to boot it.
I don't have card reader to create bootable SD card, but I have an USB, is it possible to burn to USB and copy those files to SD card.
will this work to boot Pi3?
I don't have card reader
If you mean the only thing you have to physically put the card in is a Raspberry Pi, you are out of luck. They will only boot from the SD card so that must be correctly formatted first.
USB SD card adapters are widely available (as in, around here you can find them in hardware stores and pharmacies) and shouldn't cost more than $10 USD. They are usually made for full size cards but include a further adapter you can put a micro SD card into -- check to make sure of that before you buy. If you have a laptop with a full size SD card slot (which is pretty common), then all you need is the latter, although I don't think they are sold on their own (they come with either USB adapters, or packaged with micro SD cards).