Q: My car wouldn't start after being parked in the cold for a few days

It’s clear that your battery is dead. If you want to try charging it, you need to put it on a slow charge for 12 hours or more, but I suspect even then it won’t do the job. It was probably marginal for a while and then a few nights in the deep cold were enough to finish it off. When you get the battery changed, you will want to have the charging system tested to be sure that it is OK, but since you can run after a jump, I expect you’ll find that it is all right. Be sure you have a good battery in the car before you test the charging system. If you don’t you might get a false reading. As for jump starting the car. I strongly advise against having anyone besides a professional do that. I have just finished fielding some questions for people who have done a lot of damage to their cars by hooking up the jumper cables backwards, even for a moment. The car’s electronics are very sensitive to the voltage surges that come with jump starting a car. To conveniently have your battery replaced, you can contact Your Mechanic, they can send a technician to your home or office to replace your battery and see what else might need attention.