Hi - welcome and CONGRATS!
Soooo, I don't want to scare you...but I have to be totally honest with you: you are caring for an *extremely* vulnerable and FRAGILE little kiddo here - so you need to be incredibly attentive to her. And it sounds like, from your post, that you're already getting there.
Six weeks is CRAZY young for this puppy to be away from Momma - it should be there for a full 12 weeks! That's an extremely looong time and extremely important time for a puppy's development - and your pup is going to miss out on all of that socialization etc that should be there.
First and foremost, get thee to a Vet, ASAP! Get the puppy totally checked out, vet can help with age, and you can get some help - in person- with how to feed this little one bc you may need to hand feed or whatnot. The most important thing for this puppy is nutrition, at least every 3 hours right now.
That's your first/main battle.
Also, have Nutrical on hand...you have that, yes...?
Once you get the food figured out, start googling how to socialize a pup who is taken early from Momma - there are things you'll need to do.
Good luck, keep us posted!