Often with orphaned, abandoned etc. kids, I have had to raise them in the house with a box by the heater. Once they are escaping and running all over the house, then they are strong
enough to have a nice dry bed in a draft free barn.
I agree with the replacement formula, it works if you don't have enough milk, for one reason or another, but if you can get some goat milk to mix with it, all the better. I have lost more kids on formula than on goat milk. The main thing a novice needs to know is: Keep them warm, study up on worming, and coccidiostats, use the meds reasonably, and never overfeed them.
Overfeeding them will lead to diarhea and death. And the little guys will want to eat more than they need. Rather than dilute their milk, once they have had their proper feeding, if they are still hungry, I give them all the warm
water that they want.
I normally, try to keep some goat milk frozen for just such emergencies, when you need milk and have none. Even frozen, and thawed goat milk is better than replacer formulas.
Baby animals are babies, and they need love, so you can't just pitch them out and expect good results. Even the love of other baby animals will help them to survive.
Warmth, clean food, medications for worms and coccidiosis, and some loving and they will thrive.