4 week old puppy given to us

As the post says, a 4 week old puppy given was ripped from its mother and dumped on us out of the blue. We’ve been doing some research but thought I’d ask here as well. How often should we feed, how much should they be pooping/peeing, is this going to hurt the mental development of the pup? We’re keeping her warm with a blanket and she enjoys sleeping in our hoodie pockets, but, is it fine to just make a “grul” with puppy kibble and store bought puppy milk powder? How often to feed her and how much? So many questions.