Help explaining battery power

I’ve got an arduino nano that I’ve successfully programmed to run a little combination lock for a escape room I’m doing for my kid. I bought a 3.3V battery pack but there is too little current draw and it shuts off. I got some 18650 batteries but those are 3.7 and I need to step them down? I’m not much of an electrician, is there a ready made battery pack that I can just get or is there a ready solution already sorted out that I need to follow?