In summary: If you are at someone's house. won't they have mains for a mains phone charger?Yes, they would have mains for a regular phone charger. For camping, you might want to consider a power converter.
Trevo, working with electronics and electricity is dangerous when you don't know what you're doing, even if it's just with a couple of batteries. Unfortunately it is beyond the scope of PF to teach you all about electronics and electrical safety. Thread locked.